There is a debate among SEO professionals as to how quickly acquiring links can affect the ranking of a particular site. You can find several differing opinions about the subject, and other key factors in SEO, by reading http://www.seomoz.org/article/search-ranking-factors.
In my opinion, the major factor is whether or not the links are acquired naturally. Link farms can literally give you thousands of links almost instantaneously, but so can an article which gets a lot of attention in the social media circles. So what’s the difference?
The major difference is that a social media article generates links that are related to the content on your site and thereby relevant, whereas a link farm may provide links to pages that are completely unrelated to your content. This is a significant difference, as I have mentioned in some of my earlier posts. Links that are not relevant to the content on your page are not going to be counted.
I stated in my post Linking Can Be Scary, that a good strategy is to secure 1 link a week until you have more than 20 quality links, and 2 a week thereafter. I stand by that recommendation, however there can be exceptions. When you post an article on the social media sites like http://www.digg.com it can inspire people who are interested in your content to link to you. Because this can be somewhat viral, those links may come in rather quickly but the difference is that they are natural links (relevant to your copy).
As an example, we recently had a client who signed up for a link exchange that he saw in the newspaper (without asking us first). Almost immediately after receiving the links from this program, the client dropped out of the engines. We recommended that he stop purchasing links from this program, he did and two weeks later his rankings returned to what they had been before receiving a bunch of irrelevant links.
So while it is possible to generate many links quickly, it is imperative to avoid the traps that can harm you. Ask yourself, will associating myself with this site generate links that are closely related to my content? If the answer is yes, then go ahead with it. If not then it is best to steer clear.