not a discussion for avast forum, but you can read all about it here

The Insides of Panda Cloud Antivirus
http://news.softpedia.com/news/The-Insides-of-Panda-Cloud-Antivirus-111793.shtml

Arguments against cloud-based antivirus
http://research.pandasecurity.com/arguments-against-cloud-based-antivirus/