The problem of effectively engaging the enemy with a single weapon platform at distances ranging from arms length to 1200m or more is tough enough to solve. Then there's portability, concealability (don't be the important looking fellow in the patrol- whether officer, radio, or other type of force multiplier), logistics, mission type, and so on.
Right now, it seems sniping has been broken down into several sub-sets (there's probably more, but this stuff is just off the top of my head.):
1) DMR or patrol sniper- He's the fellow who RESPONDS to enemy action, generally directed against his patrol. The US weapon here is often an accurized M16 in the hands of a "moderately" trained above average shooter, rather than a specialist. The weapon and ammo are known to be reasonably effective to 600-700m max. (The M14DMRs seem to have been problematic for logistic and "concealment" reasons.)
2) WWII or Vietnam style "Stalker/Hunter" types. Not much really going on in this format, but sniper specialists are now extremely well trained in the craft as part of their core knowledge base. Its not obsolete, just not in the forefront in the current deployments.
3) "Overwatch" or fixed emplacement sniping. Plenty of this going on. Rapid in to a locale, set up watches, observe and engage, then depart before enemy rockets or mortars are called in. More "hide and go seek" than stalking. Ranges can vary wildly, but heavy suppessing small arms fire not often needed from the sniper. Usually, he's well backed by heavies on call. Weapons vary here from 7.62mm to .338" bolt rifles as well as more recently the M110s and whatever else is being tested.
4) "Anti-Materiel" sniping- or "Oops, that armed ***** just stepped in front of the technical I was disabling with my .50" Barrett." This sort of action was most common early in the Iraq invasion. Not too sure how useful these big beasties will prove in Afganistan....
5) Special Ops- I have no idea what these folk are up to any more!
Can one weapon platform be ideal for all scenarios? Is it cost effective to train a larger percentage of the front line soldiers so that they can perform more "sniper" duties? Are the projectile throwers the limitation, or is it sighting systems, or engagement methodologies?
Too much!