I've been having the data dropping issue as well for the past few weeks. Running stock GB, rooted with safe strap, but have yet to flash a custom ROM. I thought the issue might be because I'm on a legacy Alltel plan with PRL 14012, which is way outdated...
Well, today I believe I finally found the source of what was causing the issue for me personally, from an unexpected source...Flipboard.
I've found myself glancing at it a bunch at red lights when I'm driving, or sitting in a waiting room, etc. Today I was driving though, and noted towards the end of my trip that this was the first time in weeks the phone hadn't once lost it's data connection for the entire drive. After reflecting for a moment on what, if anything, was different about this excursion, the only thing I could come up with is that I hadn't used Flipboard since I left the house. Even though my initial reaction was to seriously doubt a respectable app like that could cause such an issue, I had nothing else to go on. So, for the hell of it, I picked up my phone and fired up Flipboard...
Within 5-10 seconds of clicking it...BAM...gray 4g icon and no data would load. Needless to say, I uninstalled Flip**** right away...then reinstalled so I could comment on it in the market, then uninstalled again, and haven't dropped data at all in the last several hours. I also took note that a guy with a Droid Razr Maxx left a comment complaining that Flipboard was actually causing random reboots for him.
I don't know if any of you have Flip**** installed, or why you're having similar data issues, but if any of you do happen to have it installed, try uninstalling from the phone...not the market. Then, turn your phone off, pull out the SD card and SIM for a moment or so, put them back in, power up the device, and see if that might possibly help alleviate the constant data dropping. If I find I start dropping data again, without Flipboard installed, I'll update this post. Good luck.