There is a major problem today IMO in that the free flow of information and opinion instigated by the internet has massively disrupted our cultural landmarks, in all art forms. Prior to mass internet usage the source of critical power lay with publications mainly, and on word of mouth second. It was more difficult to create a pop/rock phenomenon by manipulating these narrow channels of influence, but it made for a longer lasting trends by keeping the range of voices narrow.
Today however, publications (in paper form at least) are declining owing to the pressures of a net savvy society and word of mouth has expanded to become a greater player in shaping our tastes. And whilst, as people here consistently point out, MTV is still around I believe that MTV and music television are essentially defunct by providing music content that doesn't go beyond reinforcement of existing trends that were created elsewhere.
Simultaneously, and understandably, with the democratisation of the internet comes the idea that everyone's largely anonymous and impersonal opinion is valid and ought to be regarded as informed, no matter the case. Whilst this is obviously a gross generalisation it seems to me to ring true when examining a forum situation and our reactions to a setting where responses move fast and our post might be outdated or unrelated by the time we finish writing it. We begin to trust certain other net users not on the basis of open settings like a forum, but more likely through personal conversation about, and here I get back on topic, things like music.
The problem is that, beyond small scale interaction via PM's or IM's there is little chance of taking someone's opinions seriously and respecting them when encountered in a forum environment. In the swirling mass of even a small message board will be hundreds (or thousands) of people whose responses we cannot begin to predict and whose outlook might be wildly different from our own.
With the demolition of physical media and traditional preference shaping tools, the public appears to be losing sight of context and developmental cycles. The majority of bands on this thread fall into two camps: New, heavily promoted and internet savvy bands and labels (e.g. linkin park, disturbed to name two heavily cited examples); and Older 'classic rock' canon bands whose entrance into modern listeners conscience stems from parents/older relatives and certain expectations ingrained into our culture ("You like ----? So you must like xxxx").
On the subject of newer bands I'd say its pretty obvious that once a band gets to a certain stage there will always be proponents and dissenters (Fanbois and Haters, if you will). Old bands on the other hand have a built in fan base that is not as fluid as today's bands. Instead, dissent usually stems from new listeners to old bands who are ignorant of the band's historical and contemporary influence on music, they (understandably) judge it against the same standards as today (hence the earlier post comparing Metallica to Dragonforce for 'shredding', even though there are wildly different components making up the music they both put out) and piss off fans who have mythologised these bands so much.
Basically, what I'm trying to articulate, is that the inherent freedoms of the internet make for a totally different environment to discuss music and art even, compared to even 20 years ago. Because really where is there a consequence-free and anonymity guaranteed forum for thought (read: 'flame wars')? der net of course