I have a very good friend that I LOVE going out to eat with. We share a fondness for bacony goodness, but that's not really why I like going to a restaurant with her. I'm very reserved, and probably go out of my way as to not draw any attention to myself in a social situation. She, on the other hand, has a loud and wild laugh, and it will cause the entire restaurant to stop and turn and look at us. Some may be embarrassed by this, and considering my talent of blending in, you'd think I'd hate it, but I LOVE IT! Her laugh is everything I wish I was. It reminds me of what being alive feels like, and reminds me that everyone has a much different voice and that's a beautiful thing.
When you start up a social media strategy for your brand, your voice should be something that is mapped out. Your voice is the actual words you are using and the tone that you create on each and every post. You may find that a very light hearted joking style works for your brand, while another brand may find that just the facts is what their audience is craving. Maybe you prefer to use profanities for funzies (this account is a great example), or peaceful and minimal word usage could be way more effective for you. Keep in mind your goals, your overall branding, then brainstorm how your desired sound fits into those.
However you choose to sound, your voice is a feature that should remain constant throughout all of your platforms. It's true that different platforms attract different users, but if you think of your voice as another aspect that defines you, you will see it's best to keep it congruent. I can always tell when one of my favorite restaurants has posted because Jeff's verbiage is just so unique.
Your voice is just another creative way to get people to remember your brand. It helps long time followers define who you are, and can draw in potential clients and followers.