I was going to put in a section about the staleness of the default layout used by many, many startups (I've certainly made many jokes about it), but I felt that would be out of scope. It
is certainly a bad tactic from a branding perspective (it's not unique), but that's a thing that can be iterated upon.
As Bootstrap becomes more popular, theme developers will flock to it (like Wordpress and Tumblr before it).