I know my program is small with only a few sites all of which are doing really really well. At the moment our affiliates are making more with revshare than they would per signup, but we don't do cross sales, popups etc and as mentioned before the members areas are pretty full and maintained.
To be honest revshare DOES NOT work for the large programs. Been there, done that, got the sticker.
The problem with small programs is they need to have a good business model for when they get more popular. All good small sites are found eventually and if they don't plan ahead for when they have hundreds, or even thousands? of affiliates, then they risk having their program 'burnt' out. Seen many of my favourite sponsors go down that road.