Yahoo and Microsoft have finally announced their search deal, after years of negotiation. In short, if the deal is approved by regulators, Yahoo Search will be powered by Microsoft Bing and Yahoo Search Marketing (aka Panama) will be powered by Microsoft adCenter.
For SEMs, you need to know when this will happen. Best case scenario, the deal will be complete in early 2010, the longest it can take for full implementation is two years. The integration will begin in the United States with search and then with search ads. The integration will then expand to other countries and regions.
The search brand at Yahoo will remain to be "Yahoo Search" but it will have a label at the bottom of the page that says "Powered by Bing." Nothing is changing now, not until they get regulatory approval, and then when they get that approval, they will begin pushing out the integration. So SEMs and SEOs have time to prepare. They won't have to worry about managing both adCenter campaigns and Panama campaigns, just adCenter (and of course, Google AdWords). I assume this means that the Yahoo Publisher Network is dead and really dead (not just in action, but legally dead).
I assume the forums will heat up throughout the days going forward. But again, this will take time, so no need to panic right now. Remember, Yahoo first started off as a directory, then they powered their search off of that directory, then worked out a deal with Google to power their search, then dropped Google for their own search engine and now is dropping their own search for Microsoft's Bing. Who knows, maybe in 5 years (even though this is a ten year deal), maybe Yahoo will go back to Google. :)