Though the questions are a bit older here, I still see no answer. Did you figure out something?
I use Titanium Backup as well, but I didn't yet dare to really delete any of the stock apps. However, I tried freezing some (one by one), and it looks safe for the following apps so far:
- MobileTV (came with the T-mobile branding)
- TopApps (came with the T-mobile branding)
- Stocks Widget (obviously belongs to the Stocks app)
- Facebook for HTC Sense
- Friend Stream
- Friend Stream Widget
- Twitter Widget
Froze them about 2 months ago, looks fine so far. Ah, besides: I'm still running Eclair (Android 2.1), so I cannot tell for sure if this applies to Froyo (2.2) as well.
Did anyone figure out some more meanwhile?