georged - 8:57 am on Jul 6, 2000 (gmt 0)
You're lucky! Make that very lucky!
The way I look at this question, ask the guy you are already working with if he'd mind. Ethically, I believe you owe him the loyalty as he is first in line. If he doesn't mind, no probs, because if you are doing well for him the next guy along will really want your service. As in, you say to him "look, if you know someone who can rank you higher, go for it."
It's easy to see how it could be very uncomfortable and awkward, though. And if business was thin, it would be tempting to take the dosh and say nothing. I think it's when business is thin that this issue is hardest to judge. When you've got mouths to feed, ethics often takes a running jump.
As far as contracts go, NDAs are very good.
Are you saying that when you get referrals, you use the clients who referred you as examples of your optimisation, and no-one else?