In theory, it could replace ebay, amazon, craigs list, silkroad, and a million smaller regional clones of these. Besides being a first really international digital trading platform, it could also establish a trusted identity foundation for all other bitcoin peer-to-peer services like messaging, financial services, collaboration, gaming, whatever else - once you've built your reputation with money, it would be costly and time-consuming to replace it, so you would at least try to keep it clean. Purchasing an established account for nefarious purposes would be pretty impossible as you can not make the seller "forget" the PK, unless you can physically put him in a cage but that is a problem from another area of human relations All in all, I have huge hopes for this.