Okay...
There are TWO apps, two different apps, for Facebook.
The Incredible comes preloaded with Facebook for HTC Sense. This can not be removed (without rooting), it's built into the ROM.
There is also Facebook for Android, which you get from the Market or AppBrain or whereever you like to get your apps.
Facebook for HTC Sense is just an interface which allows the phone to sync contacts and upload pictures.
Facebook for Android is the full application (app), which has the notifications, friends, events, etc.
They are two very different things.
If you go into Uninstaller, it is correct you will only see Facebook for Android. But YES, you can uninstall it. When it says that you "can still use the factory version" it is saying that Facebook for HTC Sense is still there and available.
I did quite a bit of research before the latest update "fix" on these because of the messed up update keeping the phone awake. I uninstalled the actual app version and only had the HTC Sense one. I also only had access to the HTC Sense interface features, not all of the Facebook App features like the full app allows.
It CAN be removed. I did it. It no longer appeared anywhere (be it the app drawer, Astro, System Panel, Android System Info, Accounts & Sync, etc). Only Facebook for HTC Sense remained.