That was the first thing I thought of as well - will the two platforms be combined?  This could have huge implications for the paid search landscape (and searching in general).  Between Yahoo and Microsoft Adcenter, Yahoo is definitely better.  I hate dealing with Adcenter - it's slow and inefficient.  And as far as searching is concerned - Yahoo is definitely better, IMO.

In October 2007 I asked about what paid search would look like in 2010 http://www.gooruze.com/questions-and-answers/discussion/101348/what-will-paid-search-look-like-in-year-2010

My comment in the post, "Either a new huge player or something drastic happening to yahoo sponsored search or MSN AdCenter."
Man, I am good!!!  hahahahah

Man...AdCenter is horrid.

All they had to do was take the best features of Google and the best features of Yahoo!...

Everytime I use AdCenter I feel like a monkey fucking a football.

My thoughts are that in the long term it will be good for search (both consumer and advertiser)  to have 2 strong players rather than 1 .

But what will it do to the internet and the impact to small start-ups? I found this post in Taipei Times, which I think provides an excellent point ... "From a start-up and investor perspective, if there are more companies trying to vie for the same businesses, there are more exits," said Bismarck Lepe, a former Google employee and now chief executive of Ooyala, a year-old video host and advertising company. "It's not great for competition if there are only two acquisition targets instead of three."

This certainly is quite big news. It will be interesting if Yahoo! accepts- think they would be crazy if they didn't. It will be good to have some real competition for Google- here's hoping it eventuates and Microhoo can really pull out all stops to give Google a run for their money!