Yep they sure have! One of our group last year when we were out with Flash tours around Limoges.
We were coming up to a roundabout in a town on our way back to base and two Gendarmes were stood by the road. I was on my S1000XR with full Akra (dB killers still in) which is pretty loud so I kept the revs low. Lady behind me on her Aprilla Tuouno (the proper V-twin one!) was pulled over, presumably as her bike sounded very fruity!
When they inspected it they noticed the holes in her exhaust where the baffles used to be bolted in and that meant she was going to get slapped with a 100 Euro fine, payable immediately or the bike would be impounded
Luckily the guy who runs Flash managed to persuade them to let her off, in his best French, but it was a close call.
She spent the rest of the holiday with some makeshift baffle ends fabricated out of baked bean tins bolted into her exhaust!