That really depends on the kind of product you're pushing. If each conversion for you is worth $100,000 and your chances of converting are 1/10,000 it would still be VERY worth it ;)
Target based ads are CPC, so its pay per click. Lets do some simple math, i send out 10,000 messages. 10% open the message, 10% click the link or whatever. Whats my cost per click assuming $1 per message.
Its actually better for the advertiser to pay for this service.
Instead of building a email list for mailing/spamming they now get targeted customer/user with their attention ( as it would land in their inbox) even without the user approving it. Fancy that!
The idea of opt-ins/opt-outs from newsletter/product emails/updates would diminish if this goes through and everyone starts using facebook again.
