I think this "straw purchase" thing is only applicable if you buy a gun with the intent of selling it to someone you know is legally incapable of purchasing it legally.
Not true. As is pointed out above, it is illegal to make a false statement on the 4473, so even if the person you are buying for is not prohibited from owning the firearm, you still commit a crime by buying it for him/her.
You are in fact then in violation of the law as you are providing a firearm to someone who is legally not eligible for legal ownership. If you buy a gun with the intent to sell it to someone who can legally own it then you should be okay.
Whether you "should" be o.k. or not is irrelevant. What matters is whether you "will" be o.k., i.e., whether you will be complying with the law. If you're buying for somebody else, you're not complying with the law, and you will NOT be o.k. if BATFE catches wind of it. I don't think they'll care much whether you think it "should" be o.k. or not.
The ATF can rule that you are a "straw purchaser" but it's not going to hold water as you can claim "I didn't like the gun and decided to get rid of it". It's one thing to charge you with something, it's an entirely different to get a jury to agree with you.
You can claim whatever you want. If there is enough evidence to make BATFE think you're lying, you risk arrest, prosecution and possibly conviction. Even if you prevail at trial, it will be very costly and unpleasant. Do you really want to go through with that?
And remember again that the statements in this forum are public and are perfectly admissible in court. The gentleman's statements that his friend bought the gun "for" him become exhibit A in their trial for conspiracy to violate various federal laws governing the sales of firearms. If they try to claim that guy 1 bought it for himself and later changed his mind before selling it to guy 2, this thread reveals them as liars and criminals who are just trying to cover their tracks.
There are many ways that prosecutors prove intent, by the way, even without admissions of the sort contained in this thread. Prosecutors and juries aren't stupid. You can claim whatever you want, but they are perfectly entitled to believe you are lying. They do it all the time. If it looks to them like a straw purchase, you can and will be convicted no matter what story you concoct.
Bottom line -- don't do it. If you want a gun, buy it yourself. If your buddy wants a gun, let him buy it himself.