TB has a new video about this:
https://www.youtube.com/watch?v=esmKdMDvSGI He takes quite a long time to basically say:
It is serious, the data revealed could contribute to further data being compromised through social engineering etc.
The breach in some cases could then allow more malicious actions such as swatting.
There are laws against this, even if it was a mistake. In obtaining customer data, Valve have a duty of care to protect it.
Valve need to up their game, and they really need to apologise (shortly after the video, though not because of it, they did apologise - check the "news" section of steam).
Anyway, he takes 27 minutes to say it, so I'm just summarising and may well have not represented that too well.