I've gotten the fake Paypal one, too, and since I've used Paypal a couple of times I wasn't sure if was real or not, so I too contacted Paypal about it. They said it was fake.
I've gotten the fake e-bay ones for quite some time. Now that I have bought something on ebay for the first time (as mentioned in another thread), I really do have an account with them, so when I got a new message supposedly from ebay, I almost opened it until I remembered that I had set up that account using my other email address.
Right before Christmas I got one supposedly from amazon that said something about a billing problem in the subject line. I use amazon regularly, but hadn't purchased anything for a while, so I went to amazon's site and checked my account there. There were no billing issues.
I never open the ones from Chase since I don't know if they're real or not, since I do have accounts with them.