Never heard of bamboo socks but various threads on MN have convinced me that my DH would like them (and just like that we are officially middle aged). I am planning to buy a 4 pack from BAM.
However, having just been without my tumble dryer for several months during a refurb, I will never (never ever never) again line dry socks or pants.
So:
YANBU - I have bamboo socks from BAM and tumble dry them all the time. They are fine.
YABU - If you tumble dry them then they will be ruined and you might as well set your money on fire.