Real Estate Agent - 20% commission back

[B-Line]

More of a research question than anything else cause I know think I'll be staying in my house for a while longer.

But I belong to a website/service that emails me with all the current listings, changes in prices, etc.
- On the website they refer a broker with the note *20% back on all commissions.

Now none of the brokers I have ever worked with, friends, business contacts, etc. have never offered any 20% commission back. So it got me thinking, should I use these brokers that advertised on the internet? They are local, I have seen their names as selling brokers as well...

Is there something here I'm missing? Cause after all 20% can be a nice chunk..

Thoughts??