Recommending headphones can never be completely right, it's a game of subjective opinion and numerous modifiers.
For those that believe that people get used to headphones (AKA, brain-in), that adds a very complicated modifier to the mix. A lot of time, people have primary and secondary headphones. Obviously they rotate between primaries from time to time, but usually people spend enough time to "retune" their ear to their primary headphone. When this happens, their view of their secondary headphones is a skewed one. The more different the primary and compared secondary headphones are, the more skewed the sound. Simply subjective can be just as inaccurate as simply objective when talking about a secondary headphone. This is, of course, especially relevant if the person receiving advice will use these as their primary headphones. For example, I went from my Ultrasones as primary to my Denons as primary. When this happened, the Denons became more bassy (I originally thought they were very bass light), and the Ultrasones became *super* bassy and bloated. Recently my Fostex's became my primary headphone (because my musical fancy seems to be metal this month, and the Fostex's are amazing with metal), and when using my Denons, they seem boomy, which they never did before.
Usually when recommending, people mix their subjective experiences (with primary or secondary headphones) with objective data and communal consensus to form the best advice, and most of the more experienced users do. This combination (and added experience) can help correct the skewed view that can result from a headphone being a secondary one.
I'm not necessarily disagreeing with the OP, I'm just saying that I don't believe objective data and communal consensus to be all bad, they can be very helpful when used correctly.
As far as recommending a headphone you don't own, I'd say it was okay as long as there is a note of full disclosure.
For example, say someone (to use the same example I used in another post) is asking for a headphone that is good for rock, open or closed, max $100. Something like the following would be acceptable (to me):
"Hey, for rock at that price range, I'd look at the Grado SR60i or Grado SR80i. They're well known for being great for rock, and should be great for the bands you listed.
However, I don't own a pair, so I'd wait for someone who does to chime in (or check out a few reviews) before getting them. Just making sure you keep them in mind before making your final decision, as I know a few people who have them and love them. :)"
Originally Posted by The D
People are more likely to be biased towards what they spent money on.
This is another thing to consider, because this is *very* true. People can be convinced that their headphones are the best things in the world, though usually this is an issue of maturity. However, if the forum is being taken over by a bunch of kids (as some are suggesting), we'll be seeing more of this. Of course, immaturity and this type of behavior is not exclusive to children and teenagers. Just more common.
Edited by Taowolf51 - 2/27/12 at 3:50pm