With the exception of Mint, the other examples were already quite successful before improving their domain name. Establishing causality in these cases is tenuous.
I seriously doubt Groupon.ThePoint.com would today be valued at over a billion dollars.
Dropbox went on a tear after their domain purchase, but I suppose it's possible they would have anyway (though I know from personal experience it was tricky to tell people about Dropbox and then try and remember the domain).
The left part of any graph that shows exponential growth looks linear. You could just as well argue that the growth has been exponential from the start.
Dropbox went on a tear after their domain purchase, but I suppose it's possible they would have anyway (though I know from personal experience it was tricky to tell people about Dropbox and then try and remember the domain).
http://www.google.com/trends?q=dropbox
(Dropbox.com was acquired in October 2009, right where growth turns from linear to exponential.)