This was taken in March of 2007 - I started using such a loose plastic bag on my cameras when my Minolta Xi's "sealed" lens got lint in it from carrying in a pocket.
A guy ("EricN2") in the UK suggested that one NOT use a zipper-seal type bag because it could trap moisture, and I agree - I buy the "Sandwich Bags" by the box at the grocery store, and it's worked a treat for me since before this photo was taken in 2007, carrying my current TZ/ZS camera in my trouser pocket at ALL times, "24/7".
In addition to keeping lint & dirt out of the camera, the smooth plastic has kept my cameras from getting worn paint. I replace the bags when they get to looking dull, or develop holes.
There is an active thread on this subject here, with more discussion: