Some of these are obvious illegal goods, and some not so obvious Travel packages and offers.

The competition is heating up among payment services, with Facebook now widely considered a potential bigplayer, and possibly Apple too. By not offering real estate rentals, timeshares, etc. Google is missing out on a fair amount of business. This is likely the driving factor behind Googles decision to allow these. On a semirelated note, Google recently announced it has made it easier to link Google Checkout with Google Base accounts. Theres a new page in the settings tab called Checkout, where you can add accounts to Checkout by entering a Checkout Merchant ID.