Panda was a reference to a Google Algorithm update. It was named "Panda" by Google and was rolled out to better improve Google search results. However it also removed or moved down many content generating websites like hubpages, triond and many others because there was alot of useless spam and poor quality content taking up top 10 search positions.
HubPages however is seem to be recovering as the number of quality content is growing and Hubpages has changed some of its standards to have good search engine ranking.
Read more here: http://en.wikipedia.org/wiki/Google_Panda