Wikipedia should definitely accept bitcoin. Wikipedia was a pioneer in online information, they should embrace and support other pioneers in technology.
It appears they have been accepting BTC for about a year, its just the link is hidden at the bottom.
I think this needs to be up near the PayPal section, that way when people see it, they will be curious what Bitcoin is and start reading up about it. Thus, not only is this thread about Wikipedia accepting BTC, which they already do. It is about spreading awareness of BTC.