Issue seems to have been resolved about right after the summer sale ended. It started far before summer sale, though. Just saying that I don't think it was directly related, but what do I know :)
Closing as it seems I'm no longer affected.
Nothing extracted yet.
The in-client browser cookie that stores my logged in state seems to time out really fast.
This is something I've noticed for the past couple of weeks. The client doesn't do any kind of preflight, instead after every five minutes or so of idle-time I'll be considered logged out. On the front page this results in an immediate reload. On other pages, like my inventory, groups, etc, it will simply end up with a an error as my profile is set to hidden. A refresh immediately fixes it since the 404 will reauthorize me, but apparently not in time to deliver a logged-in payload.
It would be nice if the client at least would keep itself logged in because this is just getting annoying. Sometimes I can't even mark a game wishlist/not-interested because by the time I'm done reviewing the store page I'll have been logged out.
In fact, when ordering a steam controller I apparently took too long and when I submitted the form I was logged out and had to start from scratch. So yeah, really annoying.
So I'm not talking about a regular browser, this is about the "native" client. I'm on Ubuntu 14.10, x86, up to date.