I'm only remotely familiar with Groupon and Mint (know of them, never used them). But both Dropbox and Facebook were building brands around those particular wo

I'm only remotely familiar with Groupon and Mint (know of them, never used them). But both Dropbox and Facebook were building brands around those particular words, yet had domains that were not the branding words (getdropbox.com, thefacebook.com). Facebook also started out initially as a college-only thing, then opened up to the world, so it's hard to say their growth was linked only to domain name changes. In either case though, (the)facebook.com could have just as easily been "allmypals.com" or something similar where the branding matched the domain name in a more direct fashion.