Interesting post! If you are really into your grammar, there is a group on facebook dedicated to your cause.
I always notice basic grammatical errors in forums, but tend to refrain from mentioning them. I think forums are quite informal and so some mistakes can go uncommented on, however mixing up forms of there, your, to, or ridiculously placed apostrophes should be acknowledged. It is evidence of declining educational standards. Many grammar rules are not that complicated to learn. Also the rise of texting, and word processing packages that fix mistakes automatically encourages laziness to develop.