I always see services here on DP that have blog networks and you can have them write articles and post your link on their 30 general blogs. Does this really help SEO? I always thought that to have any weight the link needed to be on a niche specific page. Can this give you a little boost?
A link is a link at the end of the day. A link from a general blog will definitely carry some weight. But I'd refrain from buying posts on such networks primarily because they are only made for selling posts, and will link out to all and sundry. Your backlinks number might improve, but the quality of such links isn't very great.