Our current implementation of OpenBazaar requires both Buyers and sellers to have a full node running. Though this might make sense for for sellers to have a node up to guarantee full exposure to OB's network, it might not make sense for a casual buyer to have to download a desktop application in order to buy online, because there are already existing marketplaces for that (except for smartphone users, for whom every little thing is an app on your phone).
/u/alphamystic007 said on the subreddit : "... can my online store use openbazaar as a backend while keeping my frontend the same?"
And while @SamPatt has given a very good answer on how to kind of implement that, the prospective buyer would still need to have the full OB client on their PC before hand. That's not necesarily a bad thing, but being a market at its beta stages, its highly unlikely that the buye