I agree consistency is the key but i've found if you are too aggressive in the number of links you get in relation to the size of your site you will run into problems. The size of the site and the number of backlinks you already have both seem to be factors in how quickly you can grow links. When I start link building fora site i start small and work up to a target number of links
varying anchor text is key too - don't build all your links for "blue widgets" mix it up. Add some non-anchor text links as well.
You can (and should) do link building safely. I don't see that changing for quite some time. Google is built on links and i don't think it's something they can easily shift from