[gpm]

Surprisingly not. The trick is usually to build pylons (or other cannons) such that they protect the cannons from being attacked by probes. Building them out of sight is usually too slow as a rush.

Still, he didn't do that either.

[tjoff]

In the beginning of SCII I only saw people trying to hide it. But I guess the strategy evolved, interesting.

[arayh]

Sometimes you may see a photon cannon used to deny an enemy's natural expansion to try to gain an economic advantage. Depending on the map and matchup, it may also complicate the enemy's early attempts at scouting and aggression.

Typically, you don't see more than 1-2 photo cannons, because you don't usually want to "over-invest" and lose what advantage you gain.