If you own or manage a site of a few hundred + pages. It looks like Google's changes are losing (probably temporarily) some of your pages from its index. If Google loses a lot of your pages, you must lose out in SE referrals particularly from long tail searches. The way Google works it is likely to be your deep pages that are culled.
Everything that people are reporting here has happened many times before. It happened about 12 months ago and our client's referrals were decimated, 12 months later they were at their highest ever. It is happening again now with Caffeine. I'm watching like a hawk, but I expect in 12 months time referrals will be higher than before even if I do nothing.
PS. I've been watching SEs since 94 - long before there was a Google.