Criminals use Tor same as other users. running exit node have serious risks and effects (i can't make google searches any more after that). relaying for hidden services is risky too or its safe as middle routing?
As far as I know, 'relaying for hidden services' is not optional. If you're a relay, you can be used to access hidden services.
However, being part of a circuit from a client to a HS is no different than being part of a circuit from a client to an exit and subsequently to the clear net. (If anything, there is less risk, since you're not necessarily exchanging traffic with (known) exit nodes, and the traffic you relay never hits the clear.)