I wonder why Google don't push their recommendations to a higher level, listing specifically which methods are ineffective, such as (my guess): Bookmark websites, directories of any kind, forum profiles, blog comments, avatar signature and social media fake profile.
Matt & other Googlers have been saying for many years at conferences, in online forums, blog posts, and a bunch of other communication channels that low quality links like submitting to free & unmonitored article directories are not the best way to proceed.
Basically the easier it is for you to gain the link, the less likely Google will reward you for it.
That does not mean webmasters should assume every link is bad since there are exceptions to every rule. For example posting a quality blog comment on a popular industry blog that moderates their community would probably pass some benefit. Submitting an article to a relevant industry trade association that reviews all submissions to ensure quality would also probably pass long some benefit.
A simple rule that I use for myself is only going after links that have a chance of actually driving me real traffic that will converting into a sale.
I'm using the anchor text as a test to see if the link counts, it's probably crude and over-simplified, but a start, if the site doesn't rank for the phrase used, I'm guessing it's a good article to take down.
Article submission is a terrible link building method. The articles you submit get republished on many other sites. So:
1) You end up spamming the web with duplicate content (i.e. you are creating webspam) because when you submit an article to EzineArticles, GoArticles, or some other submission site, you agree to allow other webmasters (publishers) to republish that article on their site. 2) Your site is now being linked to from a buttload of duplicate pages/webspam pages 99% of which are reposted on low quality mashup sites by webmasters too lazy to write their own content. 3) Those duplicate/webspam articles are linking to the EXACT same page(s) on your site with the EXACT same link text(s)
If generating tons of links this way from low quality sites (#2) doesn't trip a Penguin filter then the high number (and likely percentage) of backlinks pointing to the EXACT same URL(s) with the EXACT same link text(s) are likely to trip an overoptimization filter. It's a no win/high risk situation.
Same things happens with press releases.
And they're likely not just looking at the links discovered in the last X months/years... they're likely looking at ALL of your backlinks regardless of how long ago they were built. A link built that is acceptable today might be considered a "bad link" by Google 5 or 10 years from now which sucks.