I don't know about ever. Rockingham 2009 fall race gave that a run for its money. Cayuga 2008 also sucked.
I didn't go to Rockingham fall 2009, but Palm Beach was definitely worse than Cayuga . They had their big drag strip grandstand, which didnt provide a good view anyway, there was only a few people in that. They had a couple of other really really small grandstands that were nowhere near being full. they must have been 8-10 row stands and were not wide at all. really bad. There were not even really any lines to meet drivers at the autograph session. At worst, like 3 people ahead of you at any time. Cayuga, you did have to wait in lines, although the session ended quick because it started raining part way through. Those both rank up there with the worst though. The worst i've seen for a cup track was MIS 2008(The one Lofton won), rained it out to saturday morning at 9am. There was no one. They even let people that had truck tickets in to the ARCA race for free.