That may very well be, but personally, I have no objection to this at all, b/c:

- supporting Twitter does not do any damage (unless you'd argue it's subject to the mass surveillance problem and should therefor be avoided)

- you're not being locked in, you can drop it at any time without any consequences

They are doing something good for the community with bootstrap. If they get free marketing or anything else out of it they deserve it.

That "get" will quickly become a "got", as they've finally moved away from github.com/twitter to their own independent github.com/twbs repository, as was the plan for a long time: http://blog.getbootstrap.com/2012/09/29/onward/