As someone who buys referrals on ebay, I thought I'd comment.
First step - I do my research - I don't buy referrals blindly from webmasters I don't know personally or have a good feeling will be around for a long time.
Second, I figure buying referrals is an "investment" - better than one of those darned bubble things if you ask me! In some cases, you get the feeling that the webmaster is BETTING AGAINST you ever earning more back than you paid for the referrals. If you get this feeling, then you didn't follow step one.
Third, I set a price I'll pay, per referral, based on how much I think they will earn. The amount I pay depends on my confidence level from step one.
We can group the comments in this thread into two types:
- sites that are selling referrals, but doing it wrong
- sites that are selling referrals, but doing it right
All webmasters have posted what they have done right - giving gread ad packages for gold, giving out referrals on a regular basis to gold, leaving the script as is for assigning members to those without referral ids, etc.
What could they be doing wrong? Taking new members from existing members, not allowing the scripts to allocate anyone to gold, not assigning value to the gold (usually advertising, sometimes guaranteed referrals), selling referrals for more than they are worth, selling inactives, etc.
In my opinion, as long as the webmaster is doing his or her own advertising for the site, he or she can move those referrals around as he or she pleases. However, it's the programs that say "this ad was sent out for the gold members of..." that I would suggest are the ones to both join and also watch closely - that is, make sure that they mean it.
Do your research - it comes down to that. If you want to play this as a haphazard game, going gold randomly and assuming you'll win big - then you are in for a big disappointment.
I buy referrals at penniesbyemail, key-email, maniac-mail, and moneyforall. Those, I *personally* know I can trust with some certaintly of a return on my investment.

- Alex