If I remember correctly, Buterin generally advised not to install a hard cap. Collect money as much as investors are willing to invest. Who is right? Hard to say.
Not every project is suitable for such a fund-raising model. If you create something infrastructure like a means of payment, then you can scale as much as you like, and collecting funds for example on a messenger is foolish to go beyond some maximum.
Controversial analogies - I heard that the Telegram ICO is going to collect some fantastic sums already at the privat sale stage.