I guess you guys haven't had a chance to get up-close and personal with a real gorse bush. Poking around inside one would not be advisable. =)
Suffice it to say they are some pretty nasty bushes. They are extremely dense, some can be quite large in area and look at those spines. This isn't your everyday bush! Any attempt to reach one's hand into a gorse bush might result in a loss of hand, let alone the ball. =)
In order to declare a ball unplayable it must be identified according to USGA rules. There is little hope of finding the ball let alone identifying it when it makes it's way into one of these things. They are that dense. Currently the game does not have unplayable lie functionality, so you'll be sent back to the tee if you land in one of these bushes.
Avoid them at all costs!