Although it was targeted toward sites lacking good content, many quality sites were also affected by Google's Panda update last February. Now, over a month later, it appears Google has a reinclusion process in place.
Using a process similar to Google's site verification process, site owners will be able to be automatically re-included into the Google Search Results (SERP) by downloading a text file from their Webmaster Tools account. Google's crawlers will then return to those sites hit by Panda, consume the Bamboo, and reverse the effects the hungry Panda update caused.
Here is an image of Bamboo in the wild:
Unlike site verification files for Webmaster Tools and Analytics, however, there will only be a limited supply of Bamboo at large for those threatened by the Big Panda update.
Due to the limited supply of Bamboo, Google's Webmaster Central team are now concerned with link farmers creating their own Bamboo files.
Google has always had loopholes. Black hat SEOs have made a living exploiting them, paying the price, and continue on repeating the process.
Google's spam team suggests that those using some kind of farmer routine to generate their own Bamboo files for multiple sites will eventually be caught by another future update, whose name is undisclosed at this time.