I contacted a couple of customers who had recently bought Magic cards from me to let them know that I was opening an eBay store. I was a little nervous about this, thinking they might be offended at the basically unsolicited email (in other words, near-spam).
When I got this reply, it made me feel really good about my business:
"It's sellers like you that make Ebay a great place to shop! I will be checking(buying)out your store when it opens..."
Okay - maybe I'm doing something right here after all!