I agree. I turned off query caching by a mistake just some days ago, that hit the web server *really* hard! I was wondering why it was running so slow before I checked the munin graphs and saw that no queries were cached (and I could see the load building up).
If they do use a plugin-method, well, they better have an easy plugin that's plugnplay, or it won't be very useful for all the uses I'd use it for.
Memcached is nice and all, but most web sites still don't need that.