I am a big fan of Microsoft's Cashback program, as a consumer. As a searcher, I find it a bit hard to use - although it is getting better. But I have been watching the Bing forums and it just seems like this Cashback program is not only very expensive (giving cash to customers for purchases, up to 50% of those purchases) but it a big headache.
Looking at just one section of the Bing forums, I see 35% of the 20 threads there are about the Cashback program. 7 of 20 of those threads are people complaining about it. Why? Well, sometimes it is just the consumer doing it wrong (like I said, it isn't easy). Other times, it is a merchant bug and sometimes it is a Microsoft issue.
In my case, Microsoft is giving me the second half of my Cashback earnings. But not only is this costing money, in regards to the rewards, they have to deal with bugs and customers who don't even qualify for the rewards. Is all this worth the effort in order to promote Bing? That is up for them to decide, but overall, I think they have really stepped up the communication and awareness about this offering.
Forum discussion at Bing Forums.
Update: On August 19th, Microsoft sent me a check for the difference missing in my Cashback rewards. Microsoft actually used FedEx priority overnight services to send me that check, which was nice, but not necessary.