I just purchased the Bionic and already see an old problem. Some time ago (edited) I had the HTC Thunderbolt and first noticed the icon for the 3g/4g radio was gone when I unlocked the phone. Seeing as it was new I waited for a fix - never came. I went back to my Droid at the time.
Fast forward to 10 months later and the same problem different phone. When I leave my phone locked for more than 10-15 minutes and sitting on my desk, the phone disables/makes dormant the 3g/4/g radio. My radio is set to always sync in the battery settings and I have factory reset the phone.
Still happens and Verizon tech support seems unaware of the issue.
J