Badges become 'Bugged' (unobtainable) when their 'Requirements' cannot be met.
Some wizards have heard of rare, and no longer obtainable badges like 'Master of the Oasis', 'Savior of Marleybone', 'Emerald Champion', and 'Savior of DragonSpyre'.
These badges are 'bugged' because some side quests in the worlds were ELIMINATED (made unavailable) as a method of culling Excess XP. More XP was culled by decreasing the Rewards from certain Quests and Instances. And yet more was culled with the change of the Battle XP Formula.
Some badges that were bugged previously have had their 'Requirements' modified to allow them to be available (Removing flags that look for completion of quests that are no longer capable of being done). Badge such as 'Tomb Raider', 'Krokosphinx Delver', and 'Secret Shopper' are among those that have had their requirements changed to be available.
Perhaps we will one day see the return of the 'Master of the Oasis' (Completed all KT Quests), 'Savior of MarleyBone' (Completed all MB Quests), 'Emerald Champion' (Completed all MS Quests), and 'Savior of DragonSpyre' (Completed all DS Quests), as well as the release of GH Badges and a special Badge for Obtaining all Mob & Secret Boss Badges.
But, then again, Boss Badges are currently worthless if not tied into Access / Level requirements, and Badges could be so much COOLER if they had Effects.