Other than technicals, the common thread is the late stage feel the current turn of events give me, considering the size of buying required to send prices higher, we now are recruiting the largest possible entities to buy at higher prices: pension funds and soon maybe even governments and central banks.
This is definitely reminiscent of Gold back in 2010, and is a cautionary tale for people who simply want to bag hold forever, it might be very frustrating for a long time if this prognosis is correct, after the market tops in a year from now.