Just read a great article about the big four, and how they are all now competing with one another in various markets as they each branch out. I think this quote says it all
"There was a time, not long ago, when you could sum up each company quite neatly:
Apple made consumer electronics, Google ran a search engine, Amazon was a web store, and Facebook was a social network. How quaint that assessment seems today."
Check it out here
http://bit.ly/qppGbk