I like the way you are thinking... there are different approaches to linkbuilding.
I believe that different types of linkbuilding work differently for different types of websites, different types of people and different types of relationshiops.
One of the most important things to consider is the value of content on the site. If you have kickass content it can be easy to get links. Just share it via facebook, twitter, slashdot, reddit, stumble upon and the people who encounter it will pass it along to their friends/followers/ etc and some links will develop as a result. Invest in great content and your linkbuilding efforts will can be easy - but your content needs to be best-on-the-web superior stuff. Most people are unable or unwilling to produce this in quantity. This type of linkbuilding really scales because it takes no effort from you. Other people do it for you.
Once your content declines in value then you enter the "asking for links" and "building links" realms.... they are not "gifts" any more. Now you gotta work for almost every one of them, the links are not as juicy and the very best links are impossible to get. These types of links can be one-way if you have decent but not superior content. You just have to ask enough people and a few of them will link to you - as long as you have something respect able for them to link to - and you have to confine your asking to sites that are willing to link out.
Another category of links is "relationships" such as you are a member of a business group, a civic group, a tenant in a building and the landlord links to you, a donor to a library, a business in a specific town, a graduate from a school or department, or maybe your mom will link to you from her blog. These usually have nothing to do with your content and they will link to you as long as your site is not embarrassing.
Once your content and relationships decline in value to the point that nobody is really excited about you linkbuilding becomes a simple transaction...
There is a "fair trade" economy where I give you an article and you accept that content in exchange for allowing my links to remain in it.
There is a "favor economy" where you trade links, trade blog posts, etc. Nobody cares about your content they just want a link somewhere on your site.
Then comes the "purchase economy" where you pay people to link to your site.
I try to operate at the top of this list. I want to create assets on my site that people will link to because the transactions on the lower part of the list are very time consuming and expensive. The cost to scale is very high.