Took apart my sisters ipod touch 2g... (replacing the screen). Took the battery off with a small metal, screwdriver and the battery got a bit marred ("streaks" on the back where adhesive was)
But I might have a small puncture in the plastic of the battery (1/64 inch)
The plastic is also very slightly puffed up around the batt, just like it got pulled a little by the adhesive
Should I be concerned? I slapped some Electrical tape on it and around the tiny puncture...