Phone number maybe.
But if the intent of spam is to sell, it's useless without contact provisions.
Some of the useless spam is testing the waters for future selling spam or selling email addresses for future spammers.
I've noticed an increase in stock pumping spams lately. These need no reply info, as they only encourage you to go out and buy the stock. Even more clever, more are making use of imbedded graphics for the text rather than actual text itself (which is more easily spotted by filters).