This isn't really the same thing. Technically bongs, bubblers and bowls are much worse to smoke than a joint. Because these devices make it easier to "inhale the smoke", users typically get a far larger "hit" then they would from smoking a joint. This is much more damaging.

This is not accurate.

What about the ones smoking joints?

Sure. Visit Amsterdam, and you'll find most joints have filters. Of course, they aren't "proper" filters, just tubes of paper rolled up and placed in the smoking end.

They are not really supposed to be filters though, just 'roach' to make the joint easier to hold.

Yup. Doesn't really exist in american pot culture, though - from that point of view, it is a filter. I think some folks would call those rolled-up paper bits wussy or something. Then again, lots of folks here (Norway) smoke hand-rolled cigarettes without filters as well - mostly starts as a cost-saving thing and cops aren't going to give you crap for having drug paraphernalia because you have cigarette papers like they would in the states.

I can't remember if I've seen actual filters for sale in the shops in Amsterdam or not, but I'm going to guess they'd sell so long as they don't affect the buzz at all.