bill - 4:49 am on Feb 28, 2007 (gmt 0)

The people at the Yahoo! Search Blog have addressed this specifically and provided a simple way to keep these sorts of tracking URIs out of their SERPs.

Keeping Ad Tracking and Dead URLs out of Yahoo! Search [ysearchblog.com] If you don't want Yahoo! Slurp, our Web crawler to index these URLs you can use wildcards in robots.txt. For example, if you are using the parameter 'ref' to track ad sources, you can use a rule like the one below to keep your tracking URLs from being Slurped: User-Agent: Yahoo! Slurp Disallow: /*ref=YahooPublisherNetwork