I went to an NOC event last week on the subject of PayForIt... and was surprised at how dry the topic wasn't. Some scattered notes from the evening:

• Operators have implemented opt-in behaviour inconsistently;
• There are 3+ steps to making a purchase;
• Merchants don't always get a MSISDN for their customers, instead getting a unique token (but not one a future version of the API is guaranteed to honour);
• Time to implement a live service has maxed out so far at 5 days;
• 13% of users cancel payments they make during the payment process, and 7% of PayForIt billings fail - but they fail immediately, with an out of credit notification;
• Vodafone offer a higher revenue share via PayForIt than PSMS;
• Some operators can put the merchant name next to billings on phone bills;
• iPlay saw a 15% conversion rate for game downloads via an off-portal mobile site they ran; the web conversion rate was much worse;