|laziness, impatience, and hubris|
IMO I'm not sure this would be very workable if it was an option open to every user (ex anon).
My thoughts are around how subjective the area of rank is. For example a newbie (as you mention) will over rate the difficulty of their own problem whereby someone with extensive experience may underrate it.
If then there are more experienced users than inexperienced users, it may be such that it takes more and more for newbie questions to achieve higher levels of rating. Also the converse may apply.
If, however a rating system was governed by a set of criteria, (ie questions concerning map are a level 5 rating) it becomes less subjective and more objective. The problem with this approach, is there are numerous categories, and lots of grey areas. For example "How can I use map to generate HTML tables in CGI.pm?"
If it was made so that only the more experienced users could apply a rating level it may be more workable, however it would create more admin work. Also given the law of diminishing returns the more difficult the questions the more difficult it may be for a higher rating given the diverse experience of even the saints on pm.
Additionally, what would consitute each extreme of the rating system, either level 1 or level 10?
I guess at the end of the day its only a "guide", but even so, such a rating system may lead someone to miss a node they may normally read, and visa-versa.
++ for the idea and debate, but if it was put to the vote I would -- it.