According to gooseGrade.com (no idea either but find out more here) Twitter is making us grammatically retarded and spelling geniuses!  65% more grammar errors per 100 words than did non-Twitter users but roughly ½ as likely to make spelling errors**.  Kudos you!

TAKEAWAY: We should have all paid better attention in English and perhaps maths... 

Slightly mangled (but straight from the press release none-the-less) quote:

"We're not sure yet what exactly this means.  We're not prepared to say that Twitter actually improves spelling.  Perhaps the demographic of people most likely to use the Twitter service were in fact better spellers before signing up for Twitter.  The results are very interesting nonetheless and we plan on doing a much larger study involving thousands of participants in the near future," gooseGrade.com Founder and CEO, John Brooks Pounders said.

**Sample fine print stuff (or the bit where you might question if 100 people enough to draw [however initial] lofty conclusions):  The study was conducted last week and consisted of one hundred random*, English-speaking participants who either identified themselves as users or non-users of the Twitter service.  Each group was then asked to write 100 words about what they did that day.  The short essays were then graded for spelling, grammar, and punctuation errors by English Professor Ry Darby.