This is a very good question and I’m not an economist but I have my own formed opinions.

I think there are numerous interrelated issues at play.

Cheap oil is causing a ton of issues sector wise (we will likely see some bankrupcies in the US energy sector this year).

Tech companies values have risen sharply over the past four years and I think you’re going to see a pull back in general in the tech side of most peoples portfolio.

China growth is an issue and people aren’t sure how that’s going to play out and structurally how the Chinese government and its own regulators will play their hand.

Japan 0% government bond yield and negative interest rates doesn’t help.

Europe is still stagnating.

The world is still a very dangerous place with lots of global unrest and uncertainty.

In general, I think the tech sector will have negative pressure because of the very high valuations (fair) and also because of some of these secular issues (unfair).

I don’t believe something so structural like the housing market built on a ponzi scheme of CDOs on high risk debt pools are in play this time around. Which is why I believe that once things shake out a bit and the market has a chance to sputter along, it will come back to normal again.