Looking over the last 5 years, selloffs like that seen over Thurs/Fri last week (-2.8 sigma event) have been a good signal to buy Tech, momo, etc.  But it's likely different this time.

First off, MS Research lays out the case why Tech and growth are at risk – these stocks have not derated with the broader market and look rich relative to future expected earnings growth. 

There is also the well discussed crowding in Tech.  The crowding hasn't mattered so far as there has not been a fundamental catalyst to unhinge it, but recent Tech earnings may well be that catalyst.  You can't have a >$100bn loss in a well held name and not have collateral damage.  A coarse estimate of the performance of HF longs based on 13F holdings shows the last few weeks have been a ~2 standard deviation loss event, and more actively held Tech stocks vs more passively held Tech stocks suffered a 3 sigma drawdown last week.