Like you said,
It's a trend, I work at a bike shop and most people that want to buy fixies are either following the trend or just don't know how to use gears and therefore the fixie appeals to them (for reason already explained above)
Most hardcore riders already have a fixie so they are not buying them, if they needed one they would build it themselves anyway...
I'm not trying to piss anybody off, I'm a bike nut and as long as people are converting over to bikes it's cool with me but in my honest opinion, Fixies are NOT for everybody, it takes a liitle bit of talent to ride with no brakes and the city is no place to learn. You will be easily picked out as a "poser" by all the people in the know, I know this part, I work with this people. The things you don't hear are most interesting as well since you never hear from the people that developed knee issues from riding fixed do ya?
Fixed geared bikes are just like many other trends, if you can just walk into a store and buy that "cool" whatever it is you must have to be "cool" then you are too late and need to spot the next trend before you make an *** out of yourself.
Me? I'm just waiting for the tons of unused track bikes sitting in garages all over San Francisco, a couple of years from now you ought to be able to snag some crazy Japanese lug job for a couple of benjamins