The general rule I've seen around Stack Exchange is that a community is sovereign in deciding its scope¹, as long as it makes a modicum of sense. Stack Exchange employees may enforce quality requirements, for example by closing questions that are “bad subjective”. But scope — deciding what questions are on-topic or off-topic — is decided by the community, through meta discussions.

As a moderator on several Stack Exchange sites, I've always felt that it was within my mandate to crack down on low-quality questions whether the community acted or not, but that deciding the scope was solely the purview of the community. I do of course participate in debates about the scope, but I'll enforce whatever the community decides. This is what I've seen practiced on other Stack Exchange sites except sometimes on the Trilogy (SO/SU/SF).

Yet, one week into the private beta, with no prior warning that I am aware of, Robert Cartaino closed at least 15 questions (about 1/8 of the questions to date) with the only explanation, given after prompting, in a meta answer (score: 0, opposing answer scoring +19) stating

the problem with these "teach me to fish" questions is that they are on topic at Super User. Generally we do not worry too much about coincidental, overlapping scopes, but the entire premise behind this site is that most communities do not allow specific product recommendations at all.

That's a somewhat precarious premise on which to build a site — i.e. "they don't want these questions elsewhere" — but we are trying to make it work. But what we absolutely cannot allow to happen is to turn this site into an "alternative Super User"… a site where you can ask your hardware questions which also happens to allow product recommendations too. That just cannot happen.

This argument is grossly inaccurate, since the overlap would be small — this site isn't even shaping up to be about hardware in general: only about choosing hardware, not about how to install it, configure it, modify it, etc. In any case sites have been allowed that had even more overlap with existing sites, when they brought something new to the network. There's even a Stack Exchange blog post that explains that communities should stride to avoid

Scope Gerrymandering: attempting to micromanage what’s on-topic in order to avoid overlap with other sites or simply drive away users seen as undesirable.

Robert's argument also inaccurate in that some of the questions that were closed would be off-topic on Super User since they don't fit SU's restrictive definition of “computer” (e.g. smartphones are firmly off-topic there).

The argument for limiting is deeply flawed, yet this is presented as a diktat, allowing no discussion.

Some of the questions that Robert closed were reopened by the community, but Robert closed them again.

Why are we not allowed to decide our scope? To use Stack Exchange's own language, why are we not respected? As far as I'm aware, it's a unique departure from the general rule.

And why does the crackdown happen without any prior discussion?

¹ _{Excluding content that's inappropriate, e.g. NSFW.}