on scale from illegal to oh shit this is illegal, how illegal is investing in this one?
Not illegal at all.
you're funding content theft, doesn't sound too legal in my opinion
Only if the courts would first deem Vidz a 'criminal operation' and then find it such an important operation to scour the country for potential initial investors (seems like a long shot to me), you would be facing potential trouble making this investment. As far as I know OP claimed that the hosting servers are in countries of which the website complies to it's regulation, furthermore once it hits the exchanges trading Vidz would, imho, be considered an investment in.. more than funding the operation of the website; which of course is a whole lot different.
So no stress as far as i'm concerned. PureVidz is a service not an actual provider of content.