Verizon says on their webpage that the "upper 5%" that will be throttled are people using >2Gb/month. Sorry, but 2 GB is hit in a freaking hurry, even without downloading movies... My wife uses about 3 GB each month on her OG Droid, and all she goes to regularly is a messageboard and facebook...
I don't think Verizon is going to throttle just the "upper 5%". I think they're going to throttle anybody over their basic tier level for data, 2Gb, regardless of what the true upper 5% limit is, as after 2GB, they aren't making more money off that user anymore. They want people to switch to their tiered plan and drop unlimited...this is the way to try to convince unlimited users to pay more money and not be concerned with speed anymore.