This can have an adverse effect on several campaigns. One such example is if the user’s Adwords tracking URL gets crawled. This could lead to the special ad URLs being listed in Bing and the campaign receiving heightened clicks that are not relevant to the campaign.
Advertisers can manage their campaign by using robots.txt to use disallow rules. Bingbots do not crawl pages with robots.txt implemented and this is the ideal way in ensuring privacy of your pages.
Search engine optimization experts might be familiar with Bing being in the limelight for all the wrong reasons. About a year ago, Google accused Bing of copying their search results. It is important for webmasters to be aware of the possibility of their private URLs getting indexed and the need to take measures to ensure that the privacy remains intact.