Bing Webmaster Central recently confirmed how BING handles textual content in Silverlight and Flash. According to Bing, when it comes to Silverlight and Flash, the key is to use "visual content in moderation (and never at the expense of textual content)." Bing strongly suggests not using text content inside Flash or Silverlight, since many times it's invisible to search engines. According to Bing, data extraction technology as a primary method for indexation is pure "folly" and too big a gamble to take.
On a side note, we'll be discussing various topics related to "Images & Search Engines" at SES San Jose in a few weeks.