It's a toughie - I find it funny when you read things like polls on internet shopping that were taken inside shopping centres. There are a hell of a lot of people that can't go to a shopping centre and so shop online, but obviously won't be in the shopping centre to tell the poll takers in the first place. Because they shop onliine. You know what I mean, stop looking at me like that
Then again, although the people here may be biased they also have more experience about the internet than the clueless people who don't use it at all and are just taken in by the segments the BBC run on slow news days about how dangerous the internet is. If you've never used the internet but think that as soon as you go online you'll be brainwashed to be a 40 year old plumber's sex slave on the other side of the country while at the same time having all your money stolen you can be forgiven for thinking it's a dangerous place.
In short, I don't think it's biased. If anything I'd say it's more accurate. Surely the results you'd get would be less accurate if you posted this to, say, an old people's home where they have not used the internet at all in their life?
Disclaimer: See what I did there: I said old people that haven't used the internet. As opposed to the ones who have. I'm not stereotyping, me. Don't try and say I am.