Bizarre in the sense that, AFAIK, it shouldn't be necessary. For example, I've installed many, many applications (consumer, for development, etc.) and can't recall, at the moment, any others even involving the Everyone role, let alone granting it a full set of permissions.
So, what is the rationale for the .../DATA directory's security assignments?
Can I remove Everyone?
Does a member of the User group need write permission?
If so, why isn't each user's user.dir / isolated storage used instead of opening up the location under Program Files?