I have to agree. Very few people are actually buying whenever I've been in their - most go in there for the free wifi, to check emails and facebook...feel like slapping them sometimes.
Not sure why Apple still havent blocked access to social networks on their in-store wifi. I know they want to draw people in to use the machines, but surely they arent getting a sale anyway from someone who's only purpose in the shop is to post a status update.
Basic strategy, every time you take something away at the retail level you reduce numbers. Numbers equal sales, you only have to look at everybody else on this list to know why Apple does it the way they do.
Good example, how many times have you seen a sign "restrooms for customers only", yet practically everybody I know, who uses a restroom at a retail store will buy something just to feel ok about using the facillities (basic human psychology). There are always exceptions, but the basic principle applies. Let the people in for the reason they want and they will spend money, be it today or tomorrow, they are experiencing the product, the staff, the location, you name it...