A couple of years ago, I got some great advice from an attorney here in Seattle who is a bit of an 'old hand' when it comes to local startups. He had been very successfully involved with the gaming company Wizards of the Coast, of Magic and Pokemon trading card fame. He told me the one thing that stood out for him about Wizards was that they were "really good at cashing checks".
This all sounded a bit homespun to me, but he persisted, and explained that what he meant was that when someone wanted to pay them money, they made the process as friction-free as possible. If you desperately wanted to pay someone, anyone, $7.50, or whatever it cost, for a pocket-size pack of cardboard - Wizards could help you out.
For instance, Blogads sells small banner ads on, of all things, blogs. Having some experience with the product, I think that the ads deliver close to zero value to the buyer, but dammit, Blogads just made things so easy for me. They've got blogs you've heard of, they display prices, it's easy to upload your art, they take credit cards, and so on.
Even if you are not sitting on the next Magic: The Gathering, there is a valuable lesson here. Even a great product can fizzle out if it's too hard to buy, and a sub-standard one can take off if it's made convenient enough.
By the way, the Wizards guys have a new entity - Hidden City Games - hawking a new cardboard product, Clout - and I'm sure they will make a bundle with this one, too.