there have been a number of these emails going around, using official looking, but fake, pages from various banks, ISPs, and on-line merchants. The common denominator is that none of the real organizations would ask you to email back your registration information, or even email you a request to go to their website to restore your billing information. If there were truly a problem with your account, they will snail mail you at your address of record for the service or delivery. These scams are often generated in the same manner as spam (i.e., mass mailed to a spam list) without regard to whether the recipient is or is not even a "member" of the targeted phish.
I've gotten these for things I don't belong to or use, and sometimes for things I do belong to but the scam was received at an email address not used for that particular purpose. Some of them, like the ISP scams can be more easily targeted - for the recent ATT.net and Earthlink.net ones, they just filtered the spam list for addresses within the respective domain names. Others, like the eBay and Amazon.com ones, were probably sent to the entire spam list, knowing that there was a high probability that the recipient had at some point in the past bid on something or bought from amazon.
In short, if the email is trying to sell you something they want you to have - it's real. If the email is merely asking you for something they already have - it's a scam.
dw