I kind of admire Mashable because one could argue that they have in fact done what every business hopes to do - start niche and then grow to serve a mainstream market/audience. There is however always a risk that in doing so you alienate the very audience you initially set-up to serve. But if as a business you are comfortable with that then that's ok.

I do feel however that because of its undeniable success on Twitter, Mashable tends to show a little bit of bias in favour of Twitter and sometimes against Twitter's biggest rival Facebook - just my opinion.