The Wall Street Journal recently ran an article in which the chairman of Levi Jeans talked about how to care for your jeans.  The trick?  Don't wash them.  If you wash them more than twice a year, you're prematurely wearing them out.  http://online.wsj.com/article/SB10001424052748703632304575452082044100428.html
To keep your jeans from getting stinky, you're supposed to hang them up in the bathroom when you shower, and let the steam get at them.  If they get dirty, you're supposed to spot clean them.  And on the odd occasion they need a proper cleaning, lay them out flat in the bathtub with special cleaners and some vinegar.
I guess this means certain odoriferous people in our past were really just trying to keep their jeans pristine!

A University of Alberta student tested this to the extreme, by wearing the same pair of jeans for 15 months straight.  http://idle.slashdot.org/story.....-Disgusting-But-Safe.
He then got his textiles professor to test the jeans for bacteria and found them to be within healthy limits.