Thanks for your insightful comment. In fact, it depends on the industry. We do blog posts on our website Writtent.com on a daily basis (5 times a week) but we are a content marketing industry, so we would like to show our quality through a big numer of posts. However, posting sth irrelevant on your blog regularly would harm your image much more than posting something qualitative but infrequent. In fact, at some point it would probably be more resonable to pay attention to Facebook or Twitter posts because the format is a little different, and you might want to remind people of yourself (without spamming, of course) :-)
However, if you include your blog into various RSS feeds and blog directories it is nice to post daily not to get your readers forget about you and get even more new readers too.
Guest blogging does help to build relationships because when you're posted on a well-known website with good traffic, people surely get interested and share your articles in social media too.