Wow this is by far the most mature sniper thread I've ever seen, so I'll try and be just as open-minded with my opinion.
This is the way I qualify a paintball sniper:
A. Besides the beginning of the game where everyone starts at there main base, a sniper should almost never be at the main base. The only exception to this rule would be to be a "counter-sniper", or "sniper-spotter" This can be helpful in protecting the high command, because a true sniper will know how the opponent thinks and be able to prevent losses in the command chain. Besides this, any supposed "Sniper" in the main base is just a camper, not a sniper at all.
B. Yes, it is essentially true that all paintball guns with the right paint/bore match, and similar velocity will shoot about the same range. No gun will ever significantly out-range any other with the sole exception of the flat-line barrel system. So how does this define a sniper? Even without the flatline a good sniper will be a master at estimating shots. Just like real marine snipers, a paintball sniper has to take into account the wind, weather, humidty, overall temperature, distance and trajectory. A good sniper will estimate all of this instinctively, you learn this through lots of practice.
C. Concealment, now here's where I think everyone would be a paintball sniper technically if this was all you were judging by. I mean don't we all shoot from concealed positions every once in a while? The answer is yes, ambushes, good hiding spots, etc. Almost everyone who's played woodsball has shot from a concealed position. So how does a "Sniper" go above and beyond? Simple, unlike most of us who usually justr doddle around until a good fire-fight, snipers move slowly, quietly, and patiently deep into enemy territory. I know I'm too impatient to crawl 200 yards just to get 5-10 good shots, but a good sniper will do it, and then go even deeper into enemy turf. At my last scenario game my team's "Sniper" and my little brother, singlehandedly took out the other teams commander, radio guy, three body guards, and then told us the enemy's troop movements. Keep in mind he is a good one hundred fifty yards past the main battle. He even told us he got some guys casually talking to eachother as they were going down a path to reinforce the main force. He told me that one of the guys thought it was friendly fire, because of how far from the main fight it was. Now the enemy had less reinforcements, and a menace making operations hectic. If thats not beautiful stealth/tactics I don't know what is.
D. "Real Snipers" don't get the title by buying a "sniper-gun" or ghuille-suit, and they especially lose my respect if they are self-proclaimed snipers. When I hear someone say "I snipe people all day man, I hit them from like 400 feet." This just screams wannabe, first off I'm not kidding I've heard people say they hit people at ridiculous/impossible ranges. Secondly a true sniper doesn't announce it to everyone before a game, thats just asking to be hunted down and owned. The way we decided who our group sniper was by skill. My brother though not better than me in the areas I specialize in, just outclasses me in all areas required to be a sniper. We awarded him the title as our team's sniper. Even with the Title its not really official, just kind of a sign of respect for his skills.
E. Of course there are small exceptions, and its not like there is a official "sniper-council" to determine it, and people will always have there own opinions, but realize when that one good shot comes out of nowhere while your walking to the main battle and your hit in the goggle give some respect to the role of a sniper.
Do not question me, or I will sik the paintball ninja on you!!!