3 days ago, there was biggest ICO on ETH network named Status which cause DDOS attack on blockchain and lower ETH price by 20%
Previous ICO didn't cause such high Tx / hour.
The impact of status was enormous. There was around 100K TX/hour from users that want to participate in ICO Status and buy tokens.
Unfortunately ETH blockchain can handle 14 Tx/second, about 50.000 tax/hour, which was not enough and whole network become unreliable and lots of transactions failed.
As a direct result, there was a 20 % drop in price of ETH from 0.1385 to 0.115 because of network issues caused by participants in ICO. Till today ETH price didn't recover from that fall.
Due to ongoing network instability, Ethereum deposits/withdrawals are disabled on major exchanges till now.
Until ETH developers upgrade the network with Metropolis, which should in theory allow 1 million Tx / second we can expect the same kind of problems to happen again and again with every major ICO.
Despite the fact that I am a big supporter of ethereum, I do believe that such an approach with ICO will drive ETH price sharply down and will also have a very negative effect for investors.