Shouldn't a hashtag be beneath the President of the United States? Check out the handiwork of @BarackObama last night.
The complaint was based off an article in The Washington Post detailing Romney's use of a "loophole" to hide much of his investments from the financial disclosure rules required of presidential candidates. (Like many investors, Romney has a non-disclosure agreement with Bain Capital, who has most of his money, which means he doesn't have to disclose the underlying assets held by his Bain accounts.) Romney is breaking no laws and he's not the only politician to use said loophole to "hide" the sources of his wealth. Maybe a guy who wants to run the country should go beyond the bare minimum of legal requirements and maybe his opponents are right to ask where a guy who is running almost exclusively on his business acumen puts his money. (And what's in that Swiss bank account, anyway?) Or maybe Romney doesn't really owe anybody anything (if you don't like it, change the law) and doesn't really control what those account managers do anyway, so lay off.
So, yes, it's a legitimate (if somewhat tiring) political question. One that is made entirely unserious by throwing a pound sign in front of it and inviting Americans to submit their best one-liners. Any social media "expert" could have told you that tweeters would not be politely asking @MittRomney anything. Or that it would take about five seconds for conservatives to turn it back on the President with #WhatsObamaHiding. You can probably guess where that went. #BirthCertificate.