Houston PD did something like this in 2002. They arrested about 200 people in one raid. It did not turn out very well at all when the general public found out about it the next day. All charges were dropped several days later. However, it has taken 6 years to finalize all the lawsuits that were filed as a result of the raid.
http://www.chron.com/disp/story.mpl/front/5697732.html
http://www.chron.com/disp/story.mpl/front/5697732.html
