I see the need to give players their due. If they're good, they should be adulated, and rewarded. But the probowl is a bit of a popularity contest that is (a) weighted toward players that have cache, (b) weighted toward players who are on winning teams, and (c) only based on part of the season.
Balloting goes on for about 8 weeks, but misses the last 2 weeks of the season. Front-runners are always shown, so its easy to manipulate whose in and out if a group of fans vote a certain way...and what tends to happen is that some players get in based on reputation, rather than on actual production.
Now I'm not disappointed that Long and Marshall made the probowl. Good for them. But think about it for a moment. When the season still mattered, Marshall was absent from the offense. Until recently, Marshall had 3 TDs, and had dropped twice that many; he was the guy you could NOT count on when it mattered. But he had some good stats overall, and was on a pace to break 1,000 yards (which he has).
Jake Long is a shell of his former self. Yes, he's playing injured, and yes, he's still one of the best tackles in the league. But he missed most of 4 games, and parts of two others due to injury. And he was having trouble with many rushers, and allowed a higher-than-he-had-in-the-past number of sacks.
That's just my two cents.