But the medium can throw users for a loop.
We're talking "social media" here and the fact that people may not understand that "social media" is the vehicle that carries the message. "Social networking" is the message you use to make connections with like-minded individuals who share common likes, dislikes, experience, etc.
But, by default, the message's medium does say something about the user and what he or she is trying to convey. Many people use LinkedIn, Facebook and Twitter simultaneously, tweaking their messages according to the medium and the user's audience. I'm certainly not going to brag about the rivers of beer I consumed over the weekend on my LinkedIn profile but I might on my Facebook (although I probably wouldn't there either because I don't consume rivers of beer anymore - now if I was in my early 20s, maybe - because my Facebook audience may share similar experience).
So the medium kind of designates your messaging...
The struggle for some people and companies embarking on social media usage is choosing the "correct" medium to let fly their messages. All I can say is that it depends on what you're trying to accomplish. And I'd also say that it wouldn't hurt to use multiple media.
Main thing - keep your profiles updated on all of your media. And let people know what you're doing. If you're posting information, let them know your active, that you're alive. Keep posting even if you get zero response.
And don't post anything that would embarrass your mother...especially if you're looking for a job. Know why? Prospective employers are checking you out whether you like it or not.