Facebook continues to run fine for me.
You can check here: http://www.adobe.com/products/flash/about/ to see which version you should install for your Mac and OS. Note that version 10,1,102,64 is the last version available to PPC Mac users*. The latest version, 10.2.152.25 or later, is for Intel Macs only, as Adobe no longer support the PPC platform.
* Unhelpfully, if you want the last version for PPC Macs, you need to go here: http://kb2.adobe.com/cps/142/tn_14266.html and scroll down to 'Archived Versions/Older Archives'. The first one on the list, Flash Player 10.1 is the one you download. More information here: http://kb2.adobe.com/cps/838/cpsid_83808.html