No. You can get a mobile ecard with or without a data package. However, if you do not have a data package you will be charged normal carrier data rates if you have to download a mobile ecard. This is approx. one and a half cents per kilobyte.
Alltel, Sprint, & Verizon Wireless customers will get their mobile ecards like a normal picture or video message in their messaging inbox, so there is no data charge.