I had an article go to the front page of Digg a few months ago. The traffic surge took down a reasonably robust dedicated server. Instantly. I knew the article was likely to go front page and was online when it happened. Boom. Instant crash. I have a very good ISP who did a hardware upgrade on the spot and rebooted things and I was back online in fifteen minutes. The subsequent traffic was tens of thousands of hits in a few hours. Adsense income? $.17 cents on a very well optimized site. Conclusion? Digg traffic is not worth the effort or aggravation. (The article had 500+ diggs, however. I guess that counts for bragging rights.)
Social bookmarking site users are too savvy to click ads. You won't make a penny from them. The only reason to submit to those sites is for bragging rights and a shortlived high ranking backlink ...
I'm actually not all that fond of Digg and similar sites. The readers who come from those sites don't typically stay (i.e., the next day, my stats will be back to exactly normal) and they tend leave large numbers of inappropriate comments -- I really hate having to moderate every single comment when I'm getting hundreds a day because I've suddenly attracted a bunch of transient trolls from Digg. And on top of that, because my content does tend to be popular with Digg and similar sites, and we occasionally do get high-traffic-generating links, I have to plan for surge capacity. And that's spendy. And most of the time, I don't need an entire dedicated server all my own. Digg has some selling points -- I might get a few new regular readers each time we get mentioned -- but realistically, I'm not sure it's worth it. (Google News, on the other hand, is fantastic. Don't ask me why, but readers from Google News do seem willing to click on ads.) Digg could very easily mitigate the "Digg Effect" of server killing traffic, by the way, by staggering the time that articles post to the front page between servers. I assume they have a rather large server farm. It'd be nice if they were more socially conscious and did so. -- Leva