I found a post in another forum I frequent regarding holster maintenance and safety that every one should view. The link is below. The only important section is the original post with pictures, the rest degenerates rapidly.
[CCW] Glock Holster Safety Issue! - Corvette Forum
The owner had an accidental discharge with injury due to improper maintenance of his equipment. The leather of the holster became worn and flexed allowing contact with the trigger on his G19 as he was entering his vehicle. This guy was VERY stupid and very lucky that his injury was not much worse.
Personally, I like a leather / Kydex hybrid holster that covers the entire trigger and guard assembly on my Glocks. Be safe and properly maintain and use your equipment.