Two glaring weaknesses I see in this build:
1) Lack of retreat options: No + movement speed items and no real mines until 13 or so means somebody else is definately doing the tanking in this build, and if you get bum rushed by a melee DG about level 10 or so in this build, you're in serious trouble. Mark slows, but if you get jumped by 2 or 3 DGs the ability to get the heck out of there is priceless. He who fights and runs away lives to continue to collect gold and earn Kill Streak at the end of the match.
2) Such a Snipe-heavy build with no Tracking Device?
Come on. You're crippling Snipe's true power if you can't see the target to hit it, especially early on when getting Snipe kills from across the board is effective. If you're playing in no FoW custom games you don't need it of course...but where's the fun in that?
Couple changes, dump Maim I at 20, insert Tracking Device at 6 or 7 or so. Consider Journeyman's Boots instead of assassin's footguards. Likewise, once they fix negative honor, Swift Anklet would be a perfect favor item for this build.
Otherwise, very solid offensive Snipe build and a good selection of items.