When thinking about the current reach of Flash on mobile devices, I looked up some statistics (wherever I could find them).
As of today, the Android userbase has approximately 5% of the mobile market share [1].
Android 2.2 (Froyo) has approximately 4.5% of that overall 5% market share when compared to Android versions 1.5 (15%), 1.6 (20.3%) and 2.1 (59.7%) [2].
This means that Android 2.2's current market share is: 0.00225% [3]
The recently released Adobe Flash player for mobile only works on Android 2.2 [4].
So what are the odds that your target audience is going to see your Flash-based web site on their mobile device?
References:
[1] http://androidcommunity.com/android-usage-takes-5-of-us-smartphone-traffic-20090325/
[2] http://developer.android.com/resources/dashboard/platform-versions.html
[3] Special thanks to Adam Jahnke (@adamyonk) and his math on that final percentage.
[4] http://www.adobe.com/products/flashplayer/systemreqs/#mobile