Seriously?
Deliver Farmville via HTML5/CSS/Java on the iPhone and then we can talk seriously about browser based applications. This is a money driven decision, justified (with some merit, but also some bluster) using technology reasons.
I'm not a big Flash app user but my biggest beef with the Flash / iPhone debate is video. Regardless of H.264, a large number of web video is unavailable to the iPhone / iPad.
It's a shame.