By now, bitcoin is more subject to financial speculation than to anything else, it seems ... except maybe being a source of new ideas on a new field. Here is another one:
When eBay relates to PayPal, what relates to bitcoin in a similar fashion? A p2p online auction system would. Actually, to implement a p2p auctioninq/selling system (say 'bitshop', to have a working title), there are some similar problems arising when creating a p2p money transaction system. Bitshop could make use from the solutions bitcoin used for its design.
Similar tasks would be to create a timestamp (using the proof-of-work method) to determine which bid will be recognized as the final one. Another one would be to apply asymetrical cryptography keys to maintain a sellers ranking (to rate a sellers performance, the buyer has to sign the transaction -- including the rating -- with her/his keypair). This is similar to the bitcoin wallet. Other needed tasks, like p2p searches and caching of sales information (pictures, product texts), are well researched and can be easily adapted from other p2p software.
Other positive side effects of bitshop would be:
- with a rich user interface, one never again would have to wait for a slow eBay website page to build up.
- no ecological questionable server farms needed any more just to host the transaction system and to exchange a lot of unnecessary data (such as advertisments).
I would see bitshop as a sibling applicaion to bitcoin quite like eBay and PayPal as still http(s)-based web services are. I think, the latter two are dinosaurs. Let's bury them! Bitcoin doesn't have to earn the respect of online selling platforms in a long and painful process. Bitcoins design, implemented in a selling software, could easily challenge them.