Sorry, RSS. I feel compelled to intervene to get the ball rolling again.
For me, shoulder length hair is too long, but to each his own. You're right, I think it would be extremely hard to wear in an "MC" context if you have Fabio hair.
I think longish is good. I am speaking of a Southern European approach. What follows are my observations; I stick to a more austere style. Of course there are regional differences.
Since bland crewcuts are the norm in US/UK (the dominant regions on this board), having a bit more to work with gives a definite élan and instantly separates you from the pack, no matter how austere your attire. This is excellent, because hair is every bit as expressive as a fancy outfit but more subtle and integrated into one's whole. You can be the goofball in the Donegal suit, or you can be the plainly dressed but relaxed, fun-loving, long-haired guy. At least for me, there is no need to gild the lily in terms of fancy style and in your face details or colors when a rakish head of hair will do.
I am thinking of our friends Luca Cordero di Montezemolo and Roberto Mancini, whose likenesses are so often reposted here.
I think this length and style (with a loose part, pushed back) is the perfect expression of the idea and contributes in large part to their sense of presence.
Long hair is rakish. Women love it, and pencil-pushing accountants fear it. It commands a room -- not with the cold militarism of the crew cut, but with warm savoir-faire. But, you have to have the effervescence to live up to the style (have you seen Montezemolo give a talk?). No one wants long locks covering a joyless toad. Small wonder then that the style appears so often in Italy, where people have an expressive and effulgent attitude.
Long hair looks simply boss with sunglasses. Consider the man with neatly cropped hair. Sunglasses, generally a sharp, high impact item, go on top of the already sharp head and it's all too much -- the effect is pure Kianu Reeves, the businessman ready to do business, confronting the world in his Ray Bans. On the other hand, sunglasses become a symbol of sun-soaked exuberance and (somehow) ageless, timeless style when paired with long hair. They become softer, while still cool, and the whole thing has a holiday-on-the-Riviera loucheness to it. You see long hair and sunglasses and think, Ooph, there is someone on his way to have fun. And we usually are!
Men's EX and the ubiquitous Pitti images are a constant source of inspiration in this regard. Japan and Italy, two places certainly not immune to fun -- in fact, they have a monopoly on it -- know how to wear this style with ease and sophistication. Of course, the Pitti photographs suffer from that nasty issue of everyone wearing too much ridiculous bullshit, but they are a great object lesson in hairstyle. Maybe this hairstyle is inherently freeing and invites them to go a little crazy. Personally, I find that the hair is already so expressive that loading up on too much fancy stuff in the outfit just creates a clownlike effect, so I go for boring, classical clothing. But voila! The most banal and stereotyped of outfits becomes instantly worldly and fun when you have long hair -- the elegance of classicism, shorn of the dreary British stiff upper lip. Classical clothing worn in this way loses its mannered qualities (there is certainly too much of that around here) and begins to seem au courant, approachable, etc.
You know what else looks good with long hair? Tweedy odd jackets and gentle, earthtoned plaids and patterns. It's the perfect outfit for the happy sybarite, just at home in society as in nature.
We need input from the forum members mentioned in the OP. I predict Fred49 will give a one-word reply and Parker will somehow integrate graphic design into his thesis.