Choosing the right user name for your Ebay business is very important. This is something I didn't know when I started on Ebay. . . well, I sort of did know, but I was too lazy to start another account with Ebay. As a result, I "confiscated" my son's username, kawasakiguy89 just to use for a short time, never knowing I would grow my Ebay business to a powerseller status.
Kawasakiguys should be selling kawasaki products or dirt bike products, etc. I'm not. I sell baby products.
Two things have happened here though and this is just my observation. . . women don't know I'm a woman so they think it's "cute" that a guy is selling baby products. The second is, no one really cares because I have good feedback and a decent amount of feedback that they can read, so they purchase the product because they want it.
Still, it's much better to choose a username that reflects your niche product. So, if you are a scrapbook fanatic, then your username could be scrapbookmomma, or scrapbookjudy, or scrapbookingforfun. That way, your keyword, scrapbook, is incorporated in your username and people know what your ebay business will be all about. Make sense?