To Paraphrase a quote I’ve heard, “No one is more able to find new and triumphant ways to break our game than our players” (I was told this comes from someone at Blizzzard, but have never found the source myself).
Considering what makes it to the live servers (the past fractal exploits, the snowflake earring, a thousand smaller bugs and exploits) I think Arenanet should consider experimenting with their own patch test realm. The internal QA team, while necessary, is not enough to examine a game as massive as Guild Wars 2. Crowdsourcing the bugfinding process before exploits have a chance to damage the game seems like a no-brainer to me. Also, these bugs would be identified before the relevant team refocuses to their next project.