I like the idea of regenerating favors, but it becomes difficult to distinguish between the fast regenerating favors and an infrequent contacts.
I also like the idea that favors only regenerate when you (the character) do a favor back for the NPC. I have seen some GM object to style of game mechanic plot hook. I can see how a munchkin would use a favor then spend the rest of the game constantly bugging the contact/GM in an attemt to "regenerate" the favor.
Here's my current Favor/Contact ideas:
Favor: You once did a great service for a person or organization, and they owe you a favor or two. If you can contact the person or group, you can get them to repay part of the favor they owe you. This costs an action point, and you need to make a Charisma check vs DC 10. For the second and subsequent favor requests, the DC increase by 5 cumulative (second is DC 15, third is DC 20, etc). If the favor is particularly dangerous, costly, or unpleasant, the check increases by two steps and if it is all of the above it increases by three. The GM may allow the DC to go down by a step, if the plot allows you to do a favor back for the NPC.
Contact: You know a person or group of people who are in the right place. They are willing, for a price, to pass along information, access to restricted items, cut rate prices on normal goods, and occasionally provide backup. In order to use a contact, you must be able to talk to them and make a wealth check (see missing table), depending upon the nature of the deed. Contacts may be called as often as desired, but too frequent contact may make their prices go up (and ruin the point of the campaign).
The contact is pretty much the same as the D20 Modern book, except a little broader. The favors mechanic is new.