The Outer Space Treaty of 1967 makes the launching nation liable for any damage caused by rockets and spacecraft launched from their territory. With that liability comes regulation. I doubt you'll see private launches that threaten space assets of other countries.

There could be issues of space debris, similar to what most space launching countries went through. The US, Russia, and ESA have all had issues in the past of exploding upper stages due to residual propellant. We've learned how to eliminate that risk and we need to insist that everyone who launches satellites implement the lessons learned to reduce debris to the greatest extent possible.

The biggest threat to our military and national satellites isn't from 3rd party launch services but from other militaries. I hesitate to talk about this because the discussion can get very classified in a hurry. We are working to address these issues. That's about all I feel comfortable saying. There was a good article on space situational awareness as it relates to space superiority (that's what I do for a living) in the November 1st, 2004 issue of Aviation Week & Space Technology. That article doesn't appear to be available online, so you'll need to refer to the hardcopy issue.