A DigitalPoint Forums thread points to a PPC Discussions post that shows how Microsoft adCenter is converting the & to & (the HTML entity) on the fly.
So if you have tracking URLs set up that use &, then you may not be able to track them in your analytics package. Because if your analytics package or server does not translate back the & to & then the data won't be captured.
So it is important for the advertiser to know about this change and it is important for Microsoft and the other PPC engines to work with the advertiser before making these changes.
Forum discussion at DigitalPoint Forums.
