We are evaluating whether we want to continue our participation in the Medallion Guarantee Program. I'm curious if anyone has discontinued the service and what the reactions/repercussions were.

I worked for a rather small FI and we did not have a large call and we discontinued without much hoopla

You may wish to consider how it will look if you can not facilitate the sale/transfer of your own stock.

How do you get registered to offer the program? We have been getting more requests from our customers for this type of signature guarantee and need some more information about it but I'm unable to find anything online that is helpful.

It is my understanding there may be other vendors, but we use Keymark Financial Services:
http://www.kemarkfinancial.com/index.html