Google's introduction of advertising to Google Local has been a buzz within the media and blogosphere recently on a few different levels..
First, Google Local now officially offers advertising opportunities for companies that want to sponsor keyword searches. When searches are run through Google Local a 'paid-pin' (blue) will be nestled among other Local map pins (red) that match the search. The paid ads come complete with graphical logo and a small amount of information (similar to a business card listing).
I think all indicators point to ads being fused together with mashups and API sites very soon. When this happens I believe the advertising content will be relevant to the mashup or tool and won't compromise the quality and value of the content on the map. Google has perfected ad relevance in the Search, and I think they'll extend this same algorithm to Maps as well.
Here are more news links and blog discussion I have pulled together to help you understand analysis from various angles:
Google Maps API to get opt-out advertising? - ZDNet Blog, Apr.3/06: This ZDNet blog post outlines the changes in the exact wording changes in the API terms that refer to advertising.
Google Takes Its Maps Into Local Ad Market - DMNews, Apr.3/06: This direct marketing newspaper talks about the benefits to the local search ad industry.
How To Add Your Local Business Ad In Google AdWords - SearchEngineWatch.com, Mar.31/06: This is a great step by step how-to for getting your logo and business to display in Google Local. (if you're using Firefox, you may need to scroll down a bit to view this post)
Google Mellows Ad Terms For Maps - WebProNews, Apr.03/06
Google Local Ads are Official - All Points Blog, Mar.31/06
Google Local: Your Image and Text On Google Maps; My Questions - SearchEngineLowDown, Mar.31,06
Google Maps Out Its Ad Future - PCMagazine, Mar.31/06
Google local search shows image ads on maps - C|Net News.com, Mar.30/06