Welcome to Gaia! ::

I'll duel you sometime.

When I get the time, I suppose.

well it wouldn't be to hard as long as they decide on a location in towns then notify a judge to referee the duel and no one trys to cheat (not that anyone would). and have a time limit on the duel just to make it fair and then they could decide if they want a single or the best of three. Also they can choose wheather they want to run Traditional or Advanced formats.
As for Yahoo IM well they can do the same thing here except that all parties would have to have a yahoo account, but the same thing applys for this option too. It's only difficult if you make it

@shadowrider6666
I suppose one way they could do it also is with webcams, to prove that the cards they have out are in fact the cards they have out.