In one of my favorite Dilbert cartoons Dilbert describes marketing as, "That's just liquor and guessing." (I'd embed the cartoon here but United Media wants to charge bloggers for embedding).
While many engineers probably believe this is true, marketing does require experimentation, especially in new markets like the app stores. There's a big difference between guessing and testing new ideas, and what works for one type of product can easily fail for another type.
When I was doing a lot of direct mail in the late 80's (yes, I'm quite old), we tested everything in the envelope: typeface, line spacing, envelope size, color printing, special offers, pricing, and more. Then we measured the response, usually by using a different price. We tested and measured constantly, and were able to get as many as 50% of our customers to upgrade to a new version, a huge source of revenue.
One of the things I want to explore on Marketing Mobile Applications is what techniques worked, and just as importantly, what didn't for app developers.
Marketing is much more than liquor and guessing, but I'm sure that many successful app developers have come up with some great marketing ideas over drinks.