Robert Shiller sees current US Stock Market situation similar to 1928

We all know what happened in 29. Could the US Market Fall further than it did in 2008? It seems the market can only go up, until it can't. I think Robert Shiller is someone to pay attention to as he is not hype but data driven. There is no way to know how far a bubble will go until it bursts, but it would seem prudent to take chips off the table at this point.