I think the key is to build links with the natural, because google like the natural link, not directly build backlinks with excessive blast, I also continue to use tools to simplify the work, but this tool must be precise, should not make us put the website into google sandbox. I may use tool to see dofollow or nofollow blogs, such as add on firefox and see PR pages like add on Seoquake. so i still use the tool but do not overdo it.