I watched a video lately about this subject. It was a Matt Cutts (Head of spam in Google) video. He said you can create as many links as you want as long as you don’t violate Googles rules. Just don’t spam.
And here is how you don’t spam …
1. Create links from commenting on blogs and forums, but it must be relevant and helpful. Not only a link, but provide a helpful information.
2. When you create articles, write useful articles, not just articles to get a link.
So basically build links that help others, not bother them. Build where it is logical and useful.
And you don’t have to build a lot of links to rank. 1 quality link is much better than 1000 spamy links.
Also I recommend that you focus on quality links, focusing on getting at least one quality backlink a day, if youre serious about it. This can either be a guest post, a press release on a good website, a social media share on a decent active page. Stuff like that, focus on those things and you wont have to worry of the number of backlinks.