About one-third of Curves franchises have closed in the last 3 years. I don't think it has anything to do with 24/7 (other than competing companies offer 24/7) or lawsuits, but rather with a changing economy and the inability of individual franchises to remain profitable.
Here's a link to an article about the company:
http://finance.yahoo.com/news/pf_article_110004.html