Hey guys does anyone know a method where I can have scarabs zipping around in a confined area and detonating randomly, causing damage?
This is an aesthetic effect, but I also want the scarabs to actually cause damage.

Not sure if it's exactly what you're looking for but it should be a good place to start:
http://www.staredit.net/topic/5084/

Implement this method and if you need them to explode and do damage without a unit being there you could let them attacked hidden burrowed units, or possibly units that you create and remove after.

Can scarabs be given to different players?

Yes. When a scarab is moving on the battlefield, giving the reaver from which it was shot to another player also changes ownership of the associated scarab. Pretty much the same as carrier/interceptor.

Thanks Nude for posting that link! Have you found a good solution?