This deal concerns Zadkiel, a renegade angel who through devious means has recently taken over Heaven, and the Antichrist, who was last seen wandering around Wall Street. Having obtained his new position of power, Zadkiel plans on unleashing his own, cruel brand of apocalypse upon the world. However, before he can wield "ultimate power over all creation," Zadkiel must first hunt down and kill the Antichrist. You see, the Antichrist is destined to bring about Satan's biblical apocalypse in the future and Zadkiel can't have anything standing in his way of his own Armageddon.
Of course, the Ghost Riders are trying to prevent this from happening, which means that they have to find the Antichrist before Zadkiel does and keep him out of harm's way. It's an interesting situation where in order to save the world, the Ghost Riders actually have to save someone who is supposed to help destroy the world anyway.
Obviously, it is also in the Devil's interest to keep his son safe. Given this convergence of goals, he and Danny strike a deal. The latter agrees to surrender his soul for all eternity and bring the Antichrist to safety. In exchange, the former promises to provide the Ghost Riders with the location of the Gateway to Heaven and means for using it. This way the Riders can attempt to defeat Zadkiel themselves.
Unfortunately, Danny didn't seem to think the deal through.
In order for the Devil to honor his end of the deal, he must first have the knowledge that his son is safe. He can't have the Ghost Riders mount an attack on Heaven while the Antichrist is still vulnerable on Earth (though again he seems to be doing pretty well for himself in the finance world). Yet having this knowledge before offering his payment means that he has no reason to offer the keys to Heaven anymore. Sure Zadkiel is an impediment, but there could be a number of actions that Satan might take if reunited with his son. Using their collective power, he could organize an attack on Heaven himself so that he could usurp Zadkiel's power. Alternatively, he could use his son as leverage to strike a deal with Zadkiel for a joint-venture rule of Earth. Or he could actually honor the deal, but merely use the Ghost Riders as pawns to defeat the angel and then stage his attack.
What's even worse for the Ghost Riders is that they have every reason to think the Devil is lying if he does divulge information. This is why Johnny is skeptical--he believes the Devil is merely tricking Danny for his soul by offering false promises. It is clear that the fact that Danny would agree not only to bring in the Antichrist but give up his soul for information that might not even be valid is characteristic of his foolish hubris.
Were it Johnny in the situation (and assuming his soul hadn't already been sold), he would have acted differently. Johnny is a very prudent customer. He would have at the very least requested assurance of the validity of the Devil's claims prior to offering payment. He might have asked the Devil hint-type questions, i.e. to prove that the Gateway does exist (I'm not even sure he's convinced it does), to give evidence that it's in a particular area, etc. Something that would convince the Ghost Riders that they were not being set up.
This situation represents a paradox that has applications in intellectual property. In fact, it has a name! It is called the Arrow Information Paradox. What it basically states is that with information commodities, a consumer has an incentive to be as aware as possible of the value and content of any information before deciding to purchase it. Unfortunately, having knowledge makes that information less valuable. This is why it is so difficult to create information markets. For instance, suppose a musician could pay someone to write music for him. The problem is that he is not aware of whether the music will be awesome and catchy or sound like...say, Nickelback. So he asks the writer to play him a piece of the song for assurance. However, now that he knows what the song sounds like, he could reproduce it for himself and thus has no reason to purchase it.
Back to our Ghost Rider example: suppose Johnny is unwilling to sign a deal to surrender his soul unless the Devil provides more information about the Gateway to Heaven. Well, then the Devil might or might not do so depending on how desperate he is for Johnny's soul (and to see his son alive). If he does offer some conciliation, then the value of that information suddenly drops. If, for example, Johnny is suddenly made aware of the location of the Gateway, perhaps he could then find it and figure out how to utilize it himself. The deal with the Devil would consequently be worthless.
What's interesting is that in reality, there actually exist social mechanisms to help dissolve the Arrow Information Paradox. Honor is one huge element. People of certain trades or in certain groups usually adhere to a community code--a law that might be unwritten, but is generally well-known and followed. This is one reason why up-and-coming musicians don't steal other groups' music even though it might not be copyrighted. There is a code of musicians. Moreover, there is the scourge of shame and humiliation. If the public found out that one musician stole another musician's song and claimed it as his or her own, then it is very likely that he or she would face endless ridicule, which might affect sales. Basically, there are ways that society keeps the misappropriation of information in check.
Usually , the Devil has a similar social mechanism and adheres to some sort of code (thank you Tenacious D!). There is no fourth-world legal system that would punish the Devil for breach of contract, like if he backed out on the deal with the Ghost Riders. However, if people found out that Satan was a constant deal-breaker, then why would they continue to offer up their souls to him?
The difference in this scenario, however, is that there is no such social mechanism. We're talking about a situation where the outcome is most likely Armageddon. If everything goes according to plan, Satan won't be needing to make any more deals for souls. Hence, he doesn't exactly care to give the Ghost Riders accurate information, unless his ultimate plan is to use them as pawns.
Furthermore, there is no social mechanism to incentivize the Ghost Riders to honor their end of the deal. If the Devil provided Johnny with some hints about the Gateway, but Johnny figured out the rest on his own, there would be nothing to stop him from keeping his own soul.
It's this very weird stalemate that can only mean one thing: the end of the world. Unless, foolish old Danny was right all along and accidently saves the day with his lack of knowledge of information paradoxes.