while I agree with part (2) of your sentence I dont agree with (1).
I found it not fruitless to try to promote to other artists, on the contrary. I get response and true fanship from musicians and artists. And how do you know that the listener on your homepage or attending your show isn´t an artist too. So he came to leave some flyers for his own show? He came to leave a comment, that you should check out his music? Well no matter why he came, give him a reason to stay … and although he´s bent on his task, maybe he´ll stay or come back later.
It´s true that there are artists, who put up an account and then go in for promo not looking right or left, and not taking an interest in other artists. But there are more who do take an interest. Because if you are serious about finding your targeted audience you cannot help listening to other people´s music, or at least, that´s my experience.
On Soundclick I found lots of hobby, semi pro and pro musicians, who were interested, ready to buy, serious about getting and keeping in touch. And while I do my promotion, so do I get serious about getting in touch with bands I like.
I also agree with Brian: “for my sanity’s sake I prefer to target the handful of most promising leads”
that´s what I do too. But though you wrote a success story about ReverbNation in one of your blogs, I couldn´t make this site work for me. I put more effort into it than any other site, but so far I haven´t even generated visitors on my site, let alone plays or fans, and so obviously no sales. On Soundclick and iSound on the other hand, I have generated sales.
So I think you can´t say offhand, this site works, this wont.
You´ll just have to find out, which site will work for you and your band. It may be luck, or being in the right place at the right time. Who knows. So I judge these sites purely personal and emotionally, like : do I like the look and layout, do I like the way provided to get in touch with other people, what can I do for free here, how much does the site slow up my computer, how easy is it to find the right genre for my bands, how easy is it to find music that I like, … I haven´t been too far wrong, though of course it´s a lot of trial and error.

I’ve been on most of these online music sites since way back in the days of Tonos. Two things have held true through the years: (1) almost every site boils down to artists trying to promote to other artists, a fruitless venture; and (2) most of these sites hit a popularity peak and then stagnate or die. To me, building and maintaining your own site seems to be the safest way to go. Use the other OMDs as lead-ins to your site, but don’t depend on them to promote you (or even stay in business). You control your content and direction that way, and misguided management (like t61′s) cannot derail you. – Lex -

Thanks for the kind words! I’m glad you’ve found the articles useful. I’m also on iSound, Soundclick, PureVolume, and GarageBand, but never felt they warranted an article. They’ve never done anything for me, so I rarely if ever go to those sites anymore. A lot of people advise getting your music everywhere, but for my sanity’s sake I prefer to target the handful of most promising leads.

Anyway let me say thank you for all the work you put into sharing your expperience. I just read all about Jango and Taxi and it was great help deciding against them both.
I tried a few promo sites myself, not mentioned here: iSound, Soundclick, Purevolume, Reverbnation and garageband. I usually create an account, find a some 100 bands out there I like, add them and then let the site take care of itself. It´s not too much work and it pays a little. The only site that is quite different is garageband. I enjoy doing reviews! You get to hear lots of good music too.
As I am also promoting a Christian artist I will mention this site: indiegospel.org
It´s a small community of about 350 members. Still I have made more sales through Indiegospel that any other site. There´s nothing like targeted audience.
I was thinking about setting up some sites of my own, like rocktheworld or newblues. Maybe they are out there already and I just haven´t found them. But thinking about setting up and administrating a website like that just tires me out. ..