Given the recent market volatility I found this article to be extremely relevant. The article explores how Angel Investors are tending to invest less in startups because they fear market uncertainty and found that past valuations of start ups were grossly inaccurate. The article describes that some of these tech startups funded by Angele investors are valued lower than they were in earlier fundraising rounds. In turn, as Angel investors look for new companies to invest in,they fear that these younger companies are overvaluing themselves as well.
http://www.wsj.com/articles/as-angel-investors-pull-back-valuations-take-a-hit-1453337982