A few of my notes from Insider's webinar featuring Paul Larsen (credit card processing guru for subscription site industry) yesterday:#1. More than half of US consumers do NOT use a "real" card when signing up for subscriptions or memberships online. 52% are using a debit card. 15% (and growing) are using prepaid cards.This means more than half of your accounts may hit limits and be harder to retain than you suspected... unless you know how to handle things. It also means eChecks and Amex may be...