Does EBAY Have to comply with Subpoena?

My son works for a large corporation, one of the Big Three. He has been selling items and some thing he has taken out of their trash there on EBay for some time. The company it seems is having him investigated and is subpoening EBAY for all his transaction records. Is this an invasion of privacy because it includes some of his private business? How private is your business if you are selling stuff on there? Just because it's a corporation is nosing into your business, how can they invade your private life like that? Any ideas?