john_k - 5:58 pm on Jun 9, 2010 (gmt 0)

One other bit to consider is that ads using flash will make your users vulnerable to the Adobe vulnerability discussed in this thread:

Adobe Alerts Of Flash Player and Adobe Reader Vulnerability [webmasterworld.com]


If an advertiser is hacked (or less than honerable), then the door is open to get at the visitors of any website displaying their ads.