Ya you hit it on the head there. I have a new player who chose the barbarian route. His charge attacks at will alone are very powerful. That's why i was wondering about the rule on it. Rules are rules, ill have to get creative on him when i need to.
Unless the player designed a *very* unusual barbarian, his defenses are terrible. Barbarians tend to be very tough, but very easy to hit. Especially when attacks go againt Reflex or Will. (Take with grain of salt -- if he's using a spear or a heavy blade, he *might* be okay on one of those non-AC Defenses. If he's got a hammer or axe, though, they're terrible.

)
Building a charging barbarian is pretty easy. And half-orcs, goliaths, and minotaurs are exceedingly good at it. Half-orcs get the nice speed bonus, even though they're not QUITE as Barbarian-friendly as minotaurs, goliaths, and warforged.
So I would make sure to include at least a few fights with creatures that slow or immobilize based on Reflex or Will attacks. Not all the time -- this is the barbarian's strength, after all, so he should get solid mileage out of his character in most battles -- but definitely throw it in there.
One last thought: Barbarian Chargers can be seperated and killed *very* easily. (Especially Half-Orc barbarians in a 'Swift Panther Rage'... between racial bonus, the speed-boosting rage, and the at-will power's "in a rage" rider, they have a charge range of
TWENTY SQUARES.) They tend to be fast and can get in over their heads quickly if the player isn't careful. Putting a juicy target behind a hidden pit trap, throwing in a portcullis to divide the battlefield, or even having skirmishers that block his line of retreat back to the party can all really ruin a charge-happy barbarians day.
EDIT: 20 Squares requires the barbarian to move and then charge, so it is using almost their full turn. Wasn't very clear in my original paragraph.