Pay per call - great for local SMEs without websites and companies with call centres, the conversion rates are much higher when you have someone on the phone and they can ask questions, get advice and feel reassured enought to purchase.
I just tried a few terms by setting up a mock advert and it seems they are not getting many takers, either that or they are choosing not to show other bids until the launch (although it is a function that looks to be working).
I think that getting businesses interested is going to be hard, let's face it - only seo/ppc people know about it at the moment and we don't deal with the offline businesses that this is aimed at.
Bid as you would with Pay Per Click (but starting at a whopping £2 per call ($3.80)).
The adverts show a freephone number along with your details, there is no mention of your website as the idea is to get the person to call. Any URL will go to another page that has more info and a prominent 0800 number.
When anyone calls the number it costs the advertiser in the same way that Overture ads do, the simple 1p more than the person below you.
If the person calls back within 10 days there is no double billing (for Miva, other vary). The cost of the call is absorbed in the bid price but will probably terminate after 10 minutes or a set period.
That's easy enough, but..
BIG PROBLEM!
There simply are not enough freephone numbers in the UK to cope with many publishers (as you have to have different phone numbers for tracking of each advertiser * how many publishers)
I see some exclusion on the way. If you don't own a very big property then you can probably forget earning through Pay Per Call.