Blogs research

The word "blog" (combination of Web Log) can be a noun or a verb. As a noun it means a page on the internet that web users can see that can contain text, images and embedded movies and audio footage. As a verb, it means to create, change, or publish to a blog.(http://dictionary.cambridge.org/dictionary/british/blog_1)

Blogs differ from normal web pages in that they are usually interactive, in that people observing can often add comments to a post and send messages to each other or the creator via widgets. (http://en.wikipedia.org/wiki/Blog)

Blogs are used because they can provide new or interesting angles on news articles.
Also people can use blogs as a diary or running commentary of their life or an event. The blogger is often proud of his or her blog, which often becomes more than a method of communication. The blogs can reflect on life or be sentimental.
Blogs can be used in companies to either improve communication between workers or to advertise and public relations.
Some people use blogs which focus on a certain subject that they are interested in. i.e. Music blogs
(http://en.wikipedia.org/wiki/Blog)

The advantages of blogging are that people can communicate quickly with other people and comment on those posts. People can also quickly find out information about one of there interests by doing to a blog about that subject.
The disadvantages are that if people blog in their workplace, they could damage the reputation of their company. This could result in that person being fired or put on probation. E.g. A delta airlines flight attendant, called Ellen Simonetti, was fired because the comments posted in her blog "Queen of Sky: Diary of a Flight Attendant" were thought to be inappropriate.
Another disadvantage is that it can be difficult to control what is published for such a wide audience. This can lead to hateful and derogatory remarks being published. With particularly strict government rules this can result in people being imprisoned or having to leave the country. E.g. a UN representative for Sudan, Jan Pronk, was given three days to leave the country after blogging about the Sudanese armed forces. 
There is also a possibility of insults and threats being made against the author of the blog. E.g. Kathy Sierra was threatened without apparent cause after she published her blog "Creating Passionate Users"
(http://en.wikipedia.org/wiki/Blog)

Being able to leave comments on a blog is useful if a person wants to provide feedback or an opinion to what was posted. The comments could be used to ask the writer questions about the blog. If the blog was a social blog people could use comments just to talk to the writer. The comment system is useful because it enables people to contact the author even if they do not have his/her telephone number or email address. The person writing the comments does not need to have a blog or email account themselves.
However, comments in a blog can create problems for the administrator, such as inappropriate comments. It can be time consuming to properly moderate the comments.
(http://gigaom.com/collaboration/are-blog-comments-worth-it/)