The concept of throwing weapons as your central weapon is fairly unrealistic. You are often just arming your enemy, and possibly leaving yourself without a weapon. And you can never really carry enough to be effective. Most of the reasons for using one are poorly modeled by D&D.
The only systematic soldier I can think of using throwing weapons as a primary weapon is a peltast, and then the reasons are primarily cost and technology. Besides, if you were a mercenary, you wouldn't try to beat something like a Spartan phalanx at its own game. You go hurl a few javelins, earn your pay, and then beat a hasty retreat. Let the rich men with thier fancy bronze armor fight it out chest to chest.
Throwing weapons are likely to be even less effective in 4E than previous editions. A throwing weapon is semi-reasonable if you are facing just one opponent. But fourth edition is going to increase the number of opponents. Likewise, a throwing weapon makes sense if you have a chance of crippling or killing your enemy in a single blow. But 4E is going to be increasing hit points relative to damage done.