It's possible, but it would require a code change. There is no control setting for this. However, vBulletin just came out with Mobile Suite, which is a custom-branded iPhone and Android apps. I bought it and plan to work toward designing a beesource forum app.

http://www.youtube.com/watch?v=nuA5w...layer_embedded
http://www.freshnews.com/news/482678...app-ecosystem-