A couple of things to note...
There will be two events that weekend in NYS.
The event in Watkins Glen (follow the link in the OP) is being organized by the original promoter (Lang) who not only did an amazingly bad job of planning the original, but has made a disaster out of every attempt he's made at reunion concerts.
The event taking place at/near the original concert site (same property, different specific location) is an established, legitimate, permanent venue for (among other things) outdoor concerts. They have hosted numerous concerts for several years with no major catastrophes/disasters yet. Those events included 3-day events for a European group that puts on multi-day events around the globe, again with no major problems.
The original promoter approached the owners/operators of the original site and basically demanded complete control, which the owners/operators were unwilling to agree to (largely due to the promoters poor track record). So the promoter took his 'ball' and went elsewhere (or so he thinks... I believe the venue owns the rights to the name now).
IF I attend one of these events (unlikely because I hate crowds, but possible because it's the 50th Anniversary) I will be attending the event at the original site. Partly to avoid what will likely be a disaster, partly because I live 10 miles from the original site. Anyone planning to go to Bethel, NY and the Bethel Woods Performing Arts Center feel free to look me up!
