Its pretty rare for VC and PE firms to just be blatantly ripped off like a good portion of ICO investors are.
As far as I can this is due to 3 things.
1) Geography, Most VC/PE firms only invest in a particular country and know the laws as they relate to the contracts they sign with companies. This ensures that they can atleast try and go after the founders, legally speaking, if any "shenanigans" occur.
2) KYC, most will only invest after performing due diligence, which always includes meeting the team and confirming through lawyers that the team is who they say they are and they own the IP they say they do.
3) Contracts, I've participated in a few ICO's and never signed anything. I realized I was essentially giving money to a complete stranger with nothing more than an IOU from someone who I'll never meet and in many ICO cases, never have any way to find them.
Fortunetly for ICO's as a legit means to raise money these are all solvable. They just require "adults in the room.".
If you look at the successful ICO's from a professional investors angle(VC,PE) they all followed the above 3 steps.