I never received lots of spam from signing up for the 30DC. A few emails for signing up to the paid for courses over the past few years (one of which I subscribed to) but the other free stuff is worth it alone.
If your really worried, use a different email address.
@dammit get some strength and conditioning in while you work on your time on feet.
http://www.kinetic-revolution.com/30daychallenge/?sc=KRtopBar