Your paranoia is impressive. You've listed a bunch of reasons here that support Coinbase's decision to run this promotion
Coinbase is stifling the entire Bitcoin trade, especially by marking people who trade in medium to high volume. So I think they're trying to get more people marked and their info documented, it'll be a map to everyone who uses bitcoin. $75 of bitcoin is especially irresistible to people who already use cryptocurrency.
Maybe they're not stifling the entire Bitcoin trade. Maybe they're feeling victim to Xapo's security assurances. Maybe they're feeling victim to all the other options that allow people to maintain custody of their coin. Yet you assume that this is purely to document everyone using bitcoin? The effort involved int that, in something that doesn't earn them revenue, isn't logical for any business.
The only reason coinbase isn't facing any legal trouble is they give all their info to the government without any resistance, regardless of legal justification. Exactly what the government needs to get inside the bitcoin world.
They're subject to the same laws as all US based Bitcoin "banks". And those other Bitcoin "banks" aren't facing any legal trouble! Both firms have had to limit operations in some states due to American laws...what makes you think Coinbase is getting a free pass from the Feds? There's literally NO evidence to support such a claim.
A large % of people who use coinbase for a decent amount of bitcoins, even if it's just the $1k weekly limit, get multiple banks shut down due to the way coinbase reports things to banks. Doing business with coinbase can be financially crippling if you're a serious Bitcoiner who does real business of any kind.
A solid reason why Coinbase may need to create a "too good to be true" promotion!
I have never seen a company that is so malicious towards good customers, they don't even give people a fair chance to present the documents coinbase asks for if your account is suspended. They cancel all your orders, report you, and if you ask any questions about the exact documents they need they assume that is your final response and send an email saying your account is now banned.
Sounds like you're speaking from personal experience. Maybe Coinbase want's to treat their customers better...this is a great way to do it!
Is possible Coinbase could be doing this because they know that it would A) generate a spike in new wallet holders and accounts, B) generate a lot of talk on forums, and C) earn them some serious brand recognition outside of their existing market footprint? YES! YES! YES!
