Superworms can't really eat out of a bearded dragon's belly. If you haven't see the way a beardie eats a superworm, they chew them up pretty good when they ingest them!
A lot of times you hear about someone finding a deceased bearded dragon with holes chewed in the stomach - any loose superworms in the cage will quickly and readily take advantage of what they view as a food source. One of the softest spots to go in to the body is through the stomach, so a lot of times people will mistake the superworms eating the beardie as the cause of death, when it was almost always something else. Saying a superworm ate out through an adult bearded dragon's stomach is a lot like seeing vultures eating a dead cow and assuming that the vultures killed the cow.
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Little bitty baby beardies should not be eating adult sized worms, but good sized juveniles and larger beardies do not have any problems at all.
Superworms are a fantastic addition to the diet, personally I would not feed them exclusively (just like I wouldn't feed any one food source exclusively), but when fed in moderation they are definitely a fantastic addition to the diet.
-Jen