Everyone seems to have a very adamant about the car wash subject so I thought I'd throw my 2 cents in
This winter, I sold my daily driver and so my Boxster has become my daily driver. Of course this means lots of salt and crap all over my pretty car and I"ve got to say that I've been tempted to go through a quick car wash to get all that crap off.
PLEASE DON'T! All that high pressure water combined with whatever recycled crap is in the water is just asking for a sand blasting of the car. I finally found a day that was in the 50s, and hooked my hose up to my washing machine's hot water feed, and ran the hose outside. It felt great getting my car back to a non-salted state.
So, what everyone says is pretty much true I think. All the high pressure water is just asking to strip away whatever protection you have on the car. This of course, includes the high pressure washer that you wash the side of your house with. Of course, that is just my opinion.
JBG