Social media is a cheap way to market your company, services, and products. It may be a little time consuming, but it pays off quickly. You can easily double your clientele in such a short time.
Pros- fast results and it's fairly easy. There is a lot potential.
Cons- there are certain norms to follow so you need to know the social norms to be successful. More social media options come up and some are duds. You can easily waste a lot of time if you don't know what you are doing or if a social media outlet fails.

D2L is an eLearning authoring tool that many colleges use. Instructors build their course content in their shells and they can share their content easily with other instructors. It's great for discussions, quizzes, and papers/homework. You can even make students turn their papers into a plagiarism checker. It does have a blog section, but the blogs are not tied to grades or even a course. It does rooms chat rooms.
Pros- It's fairly easy to use. You can share your content and do your own course copy.
Cons- course copies are pretty touchy. Perhaps this will change in a future version. It would be nice to see blogs connected to the grade center and a course.