I am with Shiller. There are lots of indicators of historically high valuation levels. While the market can go higher, it is a great time to exercise caution.
The market lately hasn't been going anywhere fast, but has been experiencing a slow gentle climb - except for today. Well, someone slightly bumped the apple cart and wow..., it took a dive.
I have been pruning back on some weaker performers whose valuations are highly linked to high growth levels of future earnings.
IPO's are coming on strong now. Historically, Wall Street increases the IPO's at the high points of the market. I guess they are "getting um while they are hot." By the way, watch you don't burn yourself on the stove!