I have an idea of a platform where data is number one requirement. however data ( the kind I'm looking for) can be found only in companies such as Facebook and Google ..
what do you think the best way to proceed here ? do I start the platform and "invite" companies ? or I just suggest the idea to them ? I really don't know the process here.
Data is the life-blood of these businesses and intrinsic to their enterprise value. In short they will not let anyone near it, for all manner of reasons (IP, data protection, etc).
It's hard to know how to advise as we don't know much about what you are trying to achieve. In principle, I would suggest;
1) Build it
2) Prove it using a smaller, but applicable data set
2b) Ideally protect it
3) Show it to your targets, with a very clear picture of your vision, how their data would enhance the proposition, and crucially how it would be of value to them going forward.
You can look into the API's they provide to see if you can get what you need from them. Make sure you read the T&C's first to make sure your use of data is acceptable. You can also look at whether or not you can crawl the web and get the data that you need. If it's usage information, it may be available for a price. Do a proof of concept with a smaller company before you go after the larger fish.
What kind of data do you need? Maybe try approaching a start-up. They are generally eager to collaborate and you might be surprised by how much of the same value they could provide.
What is the platform intended to do, and how is it different from what these data behemoths can already do in-house?
Data - more valuable than money. Unless you have very good social connections within these entities, you're going to have a very tough time securing even a beginning dialogue. Understand they have an extraordinary number of people - just like you - banging at their door for their data. If you believe you have a novel idea and it is one, nothing will stop them from just folding it into their offerings as well, sadly. I wish I could be more bullish on this, but I cannot.
If you're wanting the open graph data for an individual Facebook user, or a single Google AdWords account, it's easy, as others have said. Otherwise it's very difficult.