Developers, is there any way to prevent collisions, so we don't have to put monitors on all our addresses? 
I am not a client developer but the simple answer is no. Private keys are randomly generated and no client has a mechanism of knowing what other addresses have been created. For example if you wanted to you could generate a private key by rolling a large number of dice and converting the results into a 256 bit number, then manually compute (using pen and a lot of paper) the public key and address. It is simply impossible for a node to know what other random numbers in the world have been used.
Still I don't believe this is a collision, not without extensive evidence to the contrary. Assuming the private key is randomly generated, the odds of a collision are simple so incredibly low that they can be considered ~0% for all intents and purposes.
