It was indeed a tarball that was collected from a Florida Keys beach, but the U.S. Coast Guard has analyzed it and found that it is not from the Gulf spill. Makes oceanographic sense. Only in the past couple of days have NOAA and French scientists independently analyzed satellite data and concluded that an eddy has swept a tendril of, in NOAA's words, "non contiguous sheens and scattered tarballs" to the near edge of the Loop Current. That's the one that swings through the Gulf and out through the Florida Strait, passing by the Keys. If the Loop Current does pick up some oil, it would be some days before it reaches the vicinity of Florida.
Nix the Florida Tarball
Richard A. Kerr