Hi Steve,
There are a whole host of changes going on with the SERPS primarily to do with falling ad revenues. Very recently it was reducing the snack pack from 7 to just 3, removing the right hand side ads and increasing the number of above the line ads to 4 to further drop organic rankings further down the page (I wrote about this on our blog http://www.digitalhound.co.uk/blog/ a while back).
The most recent developments with Adwords for instance has seen Google switch to a 30-30-80-character format from their 25-35-35-character ad format of the past 15 years. In reality, this will mean pushing the organic search results even further down the page and with consumer attention spans being what they currently are, advertisers who have trialled the new format are already reporting a 20% higher CTR than before, making Google laugh all the way the bank!
Whilst advertisers may be celebrating this new move, sadly I feel that it is cynically motivated to try and force more companies, some of whom can ill afford it to undertake a traffic paying model if they want to survive over the long term.