One more reason to never ship seeds to your grow, use your credit card, your real name, or any address easily back tracked to you. If they get any of your "meta data" from the envelope, they will be able to cross check it with other databases and know exactly who you are, what you spend your money on, where you live, who you email, etc.
If a crack down ever comes, they will be able to use this database of scanned packages to find a lot of growers. (The analysis will be done by computer, not rooms full of FBI agents studying envelopes.) If you think it can't happen, remember Operation Green Merchant. Right now we are making a lot of progress on legalization, but a backlash is very possible. The current fed policy of messing with dispensaries is small-time compared to what a real crackdown could look like. What we can all do to help make growing legal and safe is to support NORML, MPP, the ACLU and the other great organizations fighting back on our behalf.