I don't think a blanket answer can be given as to whether we allow these types of questions or not - it depends on how they're phrased (and yes I'm well aware I'm the author of some linked to there.)
Taking Can I stream 1080p video from the Pi? as an example - the question has a definitive answer, which in this case appears to be yes. I don't see how that's in the slightest bit subjective.
Similarly, while What kind of performance can I expect from using a Raspberry Pi as a webserver? has a relatively subjective title, the questions within that question are actually quite specific and again, have a measurable answer.
On the other hand, you could have questions like "Would the raspberry Pi make a good file server", with no clarification as to specific questions, and no mention of concurrent connections, load, necessary speed etc. - I believe those sorts of questions should probably be closed.
I don't see the issue in asking questions along the lines of "run a benchmark for me" either. Who says that the person asking the question even has access to a Pi to run the benchmark? It's a perfectly reasonable question to ask if someone was thinking of buying one for that purpose. Even if you take that out of the equation, then you're still assuming everyone visiting here has the necessary knowledge of how to properly run a benchmark, and how to interpret the results etc. - if we start going down the line of banning those sorts of questions, by the same logic we'd have to ban a lot of other "easy" ones too.