Not to mention online sales DO NOT reflect in store sales either. They might give you a good idea based on a hit DVD title (wedding crashers being #1 on amazon.com) but the majority of DVDs are sold at actual retailers, such as Walmart etc etc. EXAMPLE -- Serenity was #1 on Amazon.com for...
I believe season 3 is the last. I think the worry is more that since it was listed and now isn't, it's possibly hit some sort of legal snag (music rights or something... sometimes for just one song can keep a release back). It's also a fair bet that Clarissa is done for. Obviously...
Clarissa should have sold well. I was rewatching the first season and was surprised how smart that show really was. I'm all excited for the future releases. :)