I suppose it's a question of degree. If not too much CPU resource is consumed then perhaps it is an acceptable way to monetize web sites - although this would

I suppose it's a question of degree. If not too much CPU resource is consumed then perhaps it is an acceptable way to monetize web sites - although this would only work for high traffic sites, and would become less lucrative over time. There is a bit of a moral hazard though, in that it would be in the interest of the host to consume as much client CPU resource as possible, without rendering their browsing experience too unpleasant.