Choose the platform where your market is. And quickly figure out your cost of customer acquisition so you'll know how much you can afford to invest in marketing so your business model has a chance to be viable.

That either sounds obvious (and I can hear certain readers already saying "Duh...") or it sounds confusing.

So before you write it off as too obvious or too complicated - let's examine it the statement and I'll show you where the value is.

First - WHO is your market?
What will you be blogging about?
Why should they listen to you?
What value do you provide that they can't get elsewhere?

Once you figure out who your market is you'll be better able to figure out where they are.

And I don't just mean "online"... I mean specifically WHERE the are online (and by the way you really better make sure they ARE online before you even start an "online business"). Do they even have a twitter account? Do they read blogs on linkedin? If they visit linkedin but don't read the posts there - it wouldn't make any sense for YOU to post there.

Again - this might sound simple - but rest assured that many new and experienced business owners make this mistake all of the time.

The (faulty) "logic" goes like this...
"100 million people visit (whatever the site of the week is) every day - and even if I get only 1% of those people to click my article/post/ad - that would be 10,000 click! And if I could get only 1% of those people (100 of them) to spend $10.00 on my entry level product then I'll make $1000.00 per day which comes to $365,000 per year!"

If you don't get WHY that's nonsense - you really should find a business coach or mentor ASAP.

Bottom line (specifically regarding the question you asked): Deciding on a marketing platform before you know which market you are going to try to serve and how you are going to monetize your business is backwards.

I hope this was helpful. Let me know if I can be of assistance. And best of luck to you!