You may get burned by the markets - by getting back in now.
  Now selling after a crash would just be bad advise, buying when markets are largely over valued, also bad advise. Being in the market long term is the best approach, through the downs and ups as markets always return from to pre-crash values and more. With the recent heights the markets have soared to they should feel comfortable holding cash right now. Not to say there isn't any solid investments to be had, preferably dividend  paying companies as it eases the pain during market corrections. 

PS-What sandia2007 said.