When is it too much power for the street?

Once ask a Suzuki dealer how many Hyabusa's he sold.

His answer was "Sold Eight Killed Five "

There is never to much power unless owned by and asshole

My son just bought a R6 Yamaha motor for the golf buggy
watched an awesome video of a guy with a 3xx horsepower Hayabusa getting smoked by a Lamborghini.
After they stop at a light, the passenger in the Lambo says "Is that bike leaking something? Oh, no, those are tears".

The op's question is a loaded one and there is no correct answer.
yep. like others said- not too much power, just not enough brains.