Hmmmm.... I haven't lost data since the 2.1 upgrade. Don't know that had anything to do with it, but I certainly didn't change data plans. Hope they just aren't taking your money and you get some extras for the additional payments.I had this same issue. Droid would regularly wipe my exchange settings - mailbox gone. I would have to reconfigure from scratch. Until next wipe.
I finally got to tech at Verizon who said my data plan needed to be updgraded. I had an unlimited data plan, but I specifically needed "Corporate Smartphone Data Unlimited" plan. Idea being that without this check box checked Verizon (or Droid?) would see Exchange account as unauthorized and drop it. This plan costs about $10-$15 more per month than what I had.
Skeptical at first: problem is that I am not paying Verizon enough money? Also, clearly was not wiping account info every time it synched. Sometimes it worked fine.
But, three weeks after the upgrade I have not lost the setting since. This may actually be the fix. If wipe occurs again, will update this post.
Hope this helps.
Do keep us informed. I'll report if I loose the account again.
Barry