Hi,
> The best reference group I can think of would be Wikipedia users. Ideally,
> the best and cleanest way to get that sample is to publish the link on
> Wikipedia itself (e.g. on every 10'000th page or so). Do you see any chance
> to make that happen?
Please explain what you mean. Every 10,000th user page? A link to
the entire survey? How would the link being on a page distinguish
contributors from non-contributors?
If you're looking for a way to split visitors into two identical
groups, you could separate out anon IPs (mainly readers, not
contributors) that end in odd numbers from those that end in even
numbers...