My guess is your colleagues at the criminal bar would argue against this vociferously in any particular case, and it would be up to the judge to decide whether or not it's absolutely necessary to protect the security of a witness. We have heard from people who have been in these situations where they think, first, it's absolutely critical to the safety of the witness and, second, it's absolutely critical to ensure that people come forward to report crimes.
As you point out, it's not going to be the victim per se, but peripheral witnesses who help to bring these types of people to justice.