.blog domain extensions are a poor choice to run your business or blog on.
Why do I say that?
Lets look at a business called Joe's TV repair who now also fixes cell phones.
Does he rename to Joe's TV and Cell repair?
Same goes for a business located on Front Street called Front Street Dental.
The business grows strongly and moves to main street and is still called Front Street Dental.
When picking a domain extension it is also wise not to lock yourself onto one specific category. A blog for instance can get very popular and morph into a business website. So locking yourself into a niche category extension can eventually be harmful to your business.
If you plan on never changing from a blog, then sure go ahead, but the thing about life is we are always changing and we should pick or domain extension as carefully as we pick our business/domain name.
