What is SafariDAVClient doing hogging up memory?
I ran into the same problem after updating to 10.7.2. SafariDAVClient also caused CPU-spikes all the time.

Disabling Bookmark Sync in the iCloud preferences, coupled with a reboot "solved" it.

It wouldn't hurt if you would file a bugreport with Apple as well. My ID is rdar://10280447, it's still open.