This was killing my wife on her TP2, as Facebook kept switching to the mobile page, which she hates. What you do in Opera is enter opera:config in the address bar, then scroll down and click 'User Agent'. Change the numeric value for 'Spoof User Agent ID' to 4 (this masks your browser to websites, making it appear to be a Mozilla browser). Save. Then scroll a bit further down to the 'User Prefs' category, and scroll WAAAAY down to 'UAProf URL Enabled' and uncheck it. Save.
You can find out what ALL the settings do here:
http://www.opera.com/support/usingop...aini/#usermode
(Some settings do not apply to mobile devices)