Would this cause rain to leak into my car?

Getting out of my car today my shirt caught on the little piece of rubber that sits up against the window on the outside of the car and tore a chunk off.
Not sure how else to explain it so here's a picture:



Now...I have never payed attention to these little things before, but now that mine is torn...I'm wondering if that will cause water to leak into my car when it rains. Is this something to worry about? Is this something still sold?

Thanks!
Dan.

Is this the correct part?

http://johnsmustang.com/Catalog/4314/