When you for example import Seam UI example (https://github.com/seam2/jboss-seam/tree/Seam_2_3/examples/ui) to JBDS, you will face a lot of IMO unnecessary errors, which are fired by JPA validator. E.g:

"Target entity is not defined"

These rules are in most cases defined as optional attributes of JPA annotations, therefore I think the validation rules are too strict - many of them have error level by default.