I See It *all* The Time
Then/than, to/too/two, and atrocious grammar within micro-blogging. Yes, I understand you only have about 140 characters to work with. However, this is no excuse for crappy grammar and spelling. I have three kids who are into social media and they manage to sound like they're mildly educated. Throw rocks at me if you wish, but keep in mind the way you present yourself online is a snapshot into how you present yourself in the non-digital world.