In a truly competitive market, at some stage government would step in and break monopolies. For instance, they would go to Ebay and say, "look, you need to pool all your auction listings with other online auction companies, so they have access to yours and you display theirs", forcing them to actually compete on price and service.

And wikipedia is a non-commercial web app. There isn't really a blurred line - either it is for the common good or it is for profit.