From my experience working with the commercial (for-profit) conference sector, I've never seen any organiser hand over a list of email addies to anyone. They are jealously guarded as a core asset of the business.
They do quite often (heck, all the time, in fact) do "swaps", where they will mail another org's piece to their own list in return for the same. These emails will usually seek to get you to give up your contact details in return for something (a whitepaper, an interview transcript, even the conference brochure), thus adding you to the new org's list as well.
But the key point is you should always be able to unsubscribe from the first org and hear no more from them or their "marketing partners".
I think most would see it as unprofessional, bad business and cavalier with regard to privacy to actually give lists of email addresses to other organisations.
Of course, there are also some very big conference organisers out there, and they may well be pushing all sorts of unrelated events through their in-house lists. Once again, a simple unsubscribe should do the trick.
As somebody who has been tagging addresses for many years, I can say unequivocally that at least some conferences a) give email addresses up to conference sponsors, or b) are terrible at security and/or vendor selection, and so lose control of their mailing lists.
Maybe these are the sorts of things that other conference organizers cluck their tongues at when they're having drinks at conference conferences. But from the attendee side, it's difficult to distinguish which might be which.
They do quite often (heck, all the time, in fact) do "swaps", where they will mail another org's piece to their own list in return for the same. These emails will usually seek to get you to give up your contact details in return for something (a whitepaper, an interview transcript, even the conference brochure), thus adding you to the new org's list as well.
But the key point is you should always be able to unsubscribe from the first org and hear no more from them or their "marketing partners".
I think most would see it as unprofessional, bad business and cavalier with regard to privacy to actually give lists of email addresses to other organisations.
Of course, there are also some very big conference organisers out there, and they may well be pushing all sorts of unrelated events through their in-house lists. Once again, a simple unsubscribe should do the trick.