I didn't think Verizon used Sim cards. I know my 6 of my family with Droids and Verizon iPhones don't have SIMs but all of our ATT phones do.
All of the new 3G/4G LTE modems have a sim card slot that stores your account, which means no need to do ESN swaps anymore. If you get a different device you just take out the sim and insert it in the new modem.