Wrong, sites do not have PR, PageRank is assigned to individual pages within a site.
Yes, you may, but creating an article on those sites isn’t what makes it a good backlink. Your articles need to be relevant and valuable, with a lot of targeted traffic to be a good backlink. It is possible to create good backlinks on those sites, but it isn’t the site, or the domain name that makes it valuable, it is the targeted traffic and other factors that make it good.
As I stated above, the site or domain name that you create a page on has nothing to do with its value, it is the links that point at that page, and the content on that page that makes it valuable.[/quote] The page’s PR is totally dependent on the links that point to that page. It doesn’t matter which website, or domain name it is on, just which backlinks point to it.
Not necessarily a waste of time, it is a waste if you are relying solely on some kind of magic PR to emanate from the domain name, it doesn’t work that way.
Where you do sometimes benefit from posting articles on community websites is that the website may provide links from other pages of the website that point to your article and if they do you could pickup community traffic which will be beneficial and may earn you natural backlinks and bookmarks, along with targeted traffic.
Additionally, you can often benefit from participation in that community, by visiting other members pages, and commenting on them, you may spark interest in your profile that leads people to read your articles. That traffic could follow your links to your main website, thus sending you targeted traffic.