<------ voted commader.
Stealh/Sniper tactics are not ineffective at all. In Vietnam that was the dominating tactic used by the Vietnamese. The US "lost" because of of poor commanding on our side (as soon as we'd take ground, we'd leave it undefended and go to the next spot - leaving it wide open for it to be retaken), the fact the civilians could just as easily be soldiers, and the guerilla tactics.
The US also used it in the Revolutionary War against the more powerful British Army. Zee Americans won due to their tactics, they also had the support of the French initially, and the fact that they were fighting for their freedom and families while the British were fighting because their King said so.
If defending, stealth and covert ops can most definitely win it for you if it is in the correct circumstances. While it can help you win an assault - you will never win with just sniperz n' stealthz.