@deepceleron, did you get those graphs from the pool or a website that monitors pools? There was mPerth's stats which was a great resource, but it's been down a while now.
It's an unlinked-to page on a certain .lc domain pool's website.
Oh yeah! Their hashrate swings are HUGE! I've seen, in the course of a block, a swing from 650Gh->280Gh. This was a few months ago though.
I started mining here. It looks like pool hopping to me.