I have ranked one site with almost web 2.0 links, total done 50*5 pages web 2.0, but I had a link mostly on each page of web 2.0 to my site,
I have done some other links to diversity (guest posting, social bookmakrs/signals, blog comments, article submitting). Now days it will be harder, first many web 2.0 turn into no follow blogs and I face that this links now start to be marked time to time as high lvl spam.
p.s. It is not that hard to find really clean sites for guest posting, yesterday I spent about 4 hours and find really good, niche relevant blogs who accept guest posting and best out of it, it is completely free links. I can not say in total how many emails I sent, but in one day I manage to get 10 new links, all niche relevant from sites with unique and interesting articles and what is most important with visitors. I would choose to live my link on pr0 domain but with hand written and interesting content then on pr4 blog with 100 visitor day.
Most was agree for high quality article with 1 link point my site and other authority site, some asked me to link back, I refused to do it from my money sites, but I offer them links from web 2.0, links from my own pbn etc.
To find this blogs you can enter in google: submit a guest post, write for us, Submit Your Content, enter this with your niche keyword like travel, finance etc.