Problems:

1. You can't install apps to SD cards. 2.2 will allow this. 2.2 hasn't been released yet.
2. Once 2.2 is out, you still can't install apps to SD cards. Apps have to opt-in and specifically support this.
3. The location of the SD slot on many phones makes the SD expansion suited ONLY for permanent app installation. See #1 and #2
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Bruno
Twisted Melon : Fine Mac OS Software