Here's an interesting article I found via the MDN Big Blog. It's called Why MicroISVs fail to sell. It's part of an eBook from 47 Hats (not to be confused with 37 Signals!). I especially like Mistake 6: Customer as Circus Animal, in which the article encourages you not to make your customer jump through terrible hoops like the big companies do.
Of course, the take-away from this list of mistakes is that you should not be doing these things on your website and in your business. I'll leave that as an exercise for the reader.