Sigh, quickscoping isn't a problem, it is the easiest thing to stop in the world with simple inaccuracy until a little after scoping in.
The problem, as has been put by many people here, is and has been a problem in fps games for a long time. People are attracted to the sniper class because of the leet lone wolf retardness of it, and as such you see a vast majority of people playing the class in every game, usually like idiots.
Call of duty, an automatic is vastly superior to a sniper, in every way, you won't see competitive teams running around 1 shot no scopesing everyone, in game however that is consider the measure of "skill" by most of the community. They're a burden to the game in the sense of anyone actually wanting to WIN games as opposed to massaging their K
because they would do better with automatics, where a single miss doesn't mean dying.
Bad Company, bush wookies, bush wookies everywhere. Even worse, you couldn't see the fuckers for shit.
Battlefield 3, sniping heavily nerfed, glint makes them very visible. You still get a shit load of them playing the class though on every server. Worse still, with the nerfing they effectively become useless to the team, not only are they not playing the objective but they're not really getting many kills either. They're useless unless playing soflam roles or being frontline snipers with close range scopes holding corridors and medium sight lines, objectively.
The issues to address here are making sure they're not overpoweringly strong at range, but still useful, while not also being impossible to see (issues raised by BC2 and BF3). And giving them a role on the battlefield that helps the team effort.
If they're difficult to find a la BC2 then they need to be gimped in other areas, if they're easy to see and counter then they need strength and accuracy otherwise they become a useless burden to teams like BF3 where the side with the most snipers is almost always the losing side, at least in pure pub play.