Right. It's been big for the last 3-4 years. We all got that part.
Silicon Valley started busting out in the 70s when NASA set up shop there, then little companies like Xerox and HP came in, and started "breeding" other little companies like Apple, Microsoft etc.
So if by "been big for 3-4 years" you mean "been big for at least 30 years", then yes.
All snarky-ness aside, presumably you are only referring to the craze of VCs going in like a pack of Hyenas and throwing money around like its water. There are definitely some big exits (Instagram is the poster-child for that), but guaranteed for every exit, there are hundreds of failures, and the amount of lost money is mind boggling.
Like an earlier poster mentioned - I'd rather build from scratch, bootstrap and scale/iterate, all the while retaining full control and exit with a MUCH bigger piece of the pie.