Kok Waii Wong, Live Search group product manager, writing at the Live Search blog, says users "want to receive cashback instantly instead of waiting for 60 days. Well, I'm happy to announce that we've just released the Instant cashback feature with eBay. Instant cashback will be eligible for some, but not all users. Eligible shoppers will be notified online after completing a purchase on eBay."

I've asked Microsoft representatives for clarification on who is an "eligible" shopper. I'll update if I hear back.

(Update, 4 p.m.: A spokeswoman tells me via e-mail that the eligibility requirements are set by eBay. I've asked eBay for comment.)

(Update, 4:35 p.m.: "Eligibility for the instant cashback is based on a number of factors that help determine the likelihood that the transaction is legitimate (not fraudulent)," writes an eBay representative.)

Microsoft's cashback, launched in spring, connects online retailers with buyers who get a discount (Microsoft actually returns to the buyer some of the advertising revenue it collects from the retailer) if they search for the item through Microsoft's Live Search engine. Earlier this month Microsoft crowed about the performance of the cashback service.

Meanwhile, shoppers have clamored about glitches with cashback on Black Friday, particularly a deal to give shoppers 40 percent off of all HP products purchased through the Live Search cashback service. The service was down part of the day on Black Friday (though its performance today -- Cyber Monday -- would seem more important) and rather than 40 percent, some users were only getting 3 percent refunds. Todd Bishop at TechFlash has the details, including a statement from Microsoft pledging to give purchasers the full 40 percent off.

Update, 4 p.m.: Here's the statement:

"Microsoft Live Search cashback experienced an unexpected outage for several hours on Friday, November 28. If you are interested in following up on a cashback rebate for a qualifying HP purchase that you completed Friday at HP's Home & Home Office web site, we kindly request that you contact Microsoft at https://support.search.live.com. To ensure the best possible support from Microsoft, please have available your order number and the email address you provided prior to transferring to the HP site. We apologize for any inconvenience that this issue caused."

A spokeswoman also confirmed that anyone who got 3 percent, but was expecting 40 percent "WILL get the 40% if they go through the support site. Microsoft was no longer advertising 40% once the site went back up, but they are going to honor it anyway. If you did not purchase through Live Search cashback, you will NOT get the 40% back."