eBay is a gift to thieves but it's also a gift to the police. Although I've heard mixed reports about how well the two work together, it's easily searchable and because it's used for buying and selling you're quite likely to get an accurate home address from them too.
The inputting serial number idea is OK until you consider how many different goods are sold on eBay every day. I suppose they could have it apply just to bikes, electronics and motor vehicles but even then I'd imagine the logistics to be pretty tricky – it would be something along the lines of authorising a bank transaction, but it would have to be dealt with by one central server. Can't really see anyone putting this together if it doesn't increase profits, or actively harms them.
If you do want to register your property and increase the likelihood of it being returned by the police, try http://www.immobilise.com/