It's been a tough October for tech.

After the mega-cap FAANG gang led the overall market higher for most of 2018, a selloff triggered by rising interest rates and an escalating trade war hit the leaders of tech especially hard.

With two days to go in the month, the Nasdaq Composite has fallen 13%. Apple is down 7%, Facebook down 12%, Alphabet down 15%, Amazon down 23%, and Netflix down 25%.

There are a variety of reasons for the sudden slump...