A client of our company started to write a few blogs on blogger.com to build incoming links to his website. He usually wrote 2-3 comments in each blog with 10-20 links pointing to the frontpage of his website with different keywords. The blogs were quickly indexed by google (within 1-2 days) but after a while google stopped to reindex them even if some new comments were added to the blogs. Our client did a google search on the url of the blogs and found no results so he told me that google banned or blacklisted his blogs, probably because of the heavy backlinking. I checked it typing site:url to google and this way the blogs are listed on the SERP. Now I wonder what is the difference between searching for "http://mysite.com" and "site:mysite.com" - do the results come from different databases?
Interestingly if I do search on a complete sentence from these blogs, there are no results, even if the sentence is in the google cache. Did google really bannes these blogs? If so, why are they listed if I do a "site:" search? Do backlinks from banned sites or blogs negatively affect the rankings of the client's website?