Honest question - wouldn't a large stack of IOUs (say, 200k) tend to cause problems in the next investment deal? Wouldn't most investors demand to wipe that out before they are putting money in?
Maybe (I've had friends who tried to negotiated deferred salary into A-rounds). But there's also no rule saying that the IOU has to be paid back at the A-around.
Yes, investors _hate_ IOUs and often demand that they get wiped out before they invest. This is one of the reasons why Spolsky's advice is bad (in my opinion.)
If a founder can't live with a slightly unequal share distribution, he is probably going to be the kind of guy who measures office sizes with a ruler. You're doomed anyway.
It's probably good to avoid a hugely skewed share distribution, but if you really have to pay people different amounts of cash, the loser in that deal ought to get shares.