A lot of these companies have very reasonable P/E ratios now. Microsoft is sitting at around 27, Apple 25, and Facebook 15. None of those strike me as "inflated". Those are normal values for the stock market (20-25). Are investors just panicking?
I think there's some panic, yea, but the P/E doesn't tell the whole story. Take Facebook or maybe Google (just to pick on, others like Apple have their own headwinds to face) - how does advertising fair in a recession? Maybe the P/Es have retracted to look appealing, but here in about 2 years when ad revenue is down 30% those same P/Es look expensive. Personally I think if you are investing with a longer-term horizon…
It is probably the same for all large tech companies. I don't see any titans falling in the next few years.