Ivan and Abby Kirigin founded their startup, Tipjoy, to give consumers of free content a new way to pay for the stuff they really like: by leaving a tip. While the idea sounds simple enough, what the Kirigins want to do is actually far more ambitious than their quaint company name suggests. With Tipjoy they aim to exploit the commercial power of micropayments, a hip, Long Tail business concept in which consumers pay for things in tiny increments. Until now, micropayment systems have proven mos...