There are so many hoaxes going around. I have heard that you should only use plastic bottles a few times and then throw them out. There are chemicals that leach from the plastic after over use and this can be dangerous. Also, people tend to just rinse the bottles out and not wash them thoroughly which creates and spreads germs.

Although I would never put my babies bottle in the microwave. I always heated up baby bottles by putting them in a pot or bowl filled with hot water.
Microwaves don't always heat equally and a bottle after microwaving can seem warm and ok, but in the middle it can be scalding hot and burn the baby.
Not worth taking a chance.

Kate