Does attaching patches to your leather compromise its integrity? I'm taking them to someone to stitch on, but how do I know they'll hold up in the event of ground contact?!?!?

Biker Boyz?  Remember, gangs incourage group mentality and reckless behavior.

Hey, I'm just talking out of the top of my head, but I would wager that the area where the patch is sewn on will be stronger than any of the other joined seems on the jacket but not quite as strong as it was before it was perforated.  But. . .since the seems where the sleeves meet are strong enough, the area where the patch is sewn should be  .

Patches usually just get shredded and fall off. The stitching that goes into a patch should not be nearly as strong, nor as many threads, as the stitching used in the rest of the jacket. I have my father's 104th infantry patch on one of my jackets, but now I'm going to take it off because I don't want to ruin it.

If perforated leather is safe enough to crash in, then a patch isn't going to compromise the safety of the leather...  The thread holes are MUCH smaller and there are fewer of them.

The only problem you might have is if the patch got caught up on something...  But, like scratch said, I imagine it would simply rip off.

Speaking as someone who works in a bike leather shop, and has seen countless crashed jackets, I would say that it's not a problem at all. If your jacket is made from a thick enough skin and is indeed a real bike jacket with double stitching and what not, the leather is not going to rip no matter how many patched you've got on it. I had one guy who crashed going pretty fast (can't remember the exact speed) wearing a jacket, and a vest over top of the jacket with his club patch on the back. The patch was blackened, fraying and coming down in the corners, and the vest was shredded pretty bad, but still in one piece. The guy wore it as a reminder of what happened and how easily it could happen again. This was also a bike specific vest made out of the same high quality leather that our jackets are made of.
If you want proof, find a scrap piece of leather and punch a bunch of holes through it with a nail. Now pull on it as much as you like and you can see that it doesn't weaken it at all. When I first started working with leather I was surprised by how strong it is. I guess that's why they make protective jackets out of it. 

I have a fully perforated race suit that I have been down in twice at 60+. At least I have matching sides now. No problem with the leather, just some worn stiching. 

Anyone know where I can get Kevlar thread? 

thanks for the advice guys - yeah these are patches for my new perf'd racing suit - i have a few things I want to attach, but didn't want to compromise the $1000 price tag the thing cost me!

Well your not going to compromise the leather but patches do destroy resale value. Then again, why would you be selling the suit you just got. I donno, but just thought I'd inform you of what I know.

I'm curious what the patches are.

I've sewn on several to various bits of leather...never had any problems myself.