In pure marketing terms, you can build a brand around anything, but it's always smart to have a name that resinates well with your primary target market, and I'm not sure that one would stay on the tips of people's tongues for long.
In regards to ebay, well if you are only going to trade with that name on ebay, it's not overly important what id you go by, but you have to think ahead to where you want to be trading in 5, 10 years time.
If you have a desire to build your own website, and build your business up, then you should start building your brand from day one, and that means going with a name that you can register legally.
Getting that name as your URL isn't that important, so that's not something I would be concerned about early on. Yes, always nice to have your business brand as your URL, but not so easy to do these days.