I don’t think this is a huge problem with the ICO model generally. Immediate liquidity makes it easier for the weak projects to fail quicker (entrepreneurs can cash out and exit very easily), but the entrepreneurs of the strong projects (i.e Ethereum) are going to maintain ownership stakes and continue to be motivated to build at protocol level by increasing demand for the token.

Also for many projects, vesting schedules are being implemented at the protocol level to restrict founder liquidity (see Zcash, Steem).