Too many tournaments to fill them all up (since everyone will be chief of a self-titled tournament), too many games causing too big a stress on the server(s), not exclusive enough due to 100's of tournaments starting each day, silly banden tournaments like one for members with 0-100 ratings, et cetera.
I don't want to cause any arguments, but I can't see how multiple tournaments can cause *that* much stress unless the site is written incredibly strangely. Mind you - I haven't actually written a site like this (yet), so shouldn't really comment 🙂
Is the whole thing running on one server then? I would have imagined it would be pretty easy to migrate it to an apache cluster and a MySQL cluster to scale it up - but then there are always tricks like loading MySQL into memory and running the Zend optimiser/cache/compiler doobries to really make it shift...
I'll stop coming up with ideas - I know from my own work how annoying it is 🙂