In my very narrow niche, one site that has been around for a long time but doesn't have a whole lot of links leapfrogged several sites ahead of it that have more links.
I've seen an identical occurrence with a competitor site in my own niche. The site has been around for years. It doesn't seem to get many links, but the existing links are old. It has bounded above many of the rest without developing new links, without being mentioned in social media (unlinked citations), without having much content (21 thin pages, that's it), and without having any new content (a given since they only have 21 pages. What's more, they don't blog, don't have a facebook page, don't tweet, yadda yadda. It simply seems to be a function of age.
I would be tempted to say that what is powering the site is due to user behavior, such as has been mentioned in other threads lately (i.e. bounce rate, time spent on site). However, those 21 pages are verrrrryyy thin and unsatisfying. I just don't think user behavior is the engine. I think its just a function of domain age and age of links.
Which brings me back to those question?
Is it still worth pursuing links? I would hope so.
Do we have to wait around forever for even the cleanest additions to our back links to have any push effect at all?