Subject: Can particle accellerators implode 'in our face' ?

As particle accelerators have become increasingly powerfull some 
sciencetists have expressed concern that we may create particles 
that may affect surroundings in undesiable ways. Some scientists 
have even suggested that we may create a black hole by accident 
which would be very unfortunate for all of us I imagine.
 From my limited knowledge of high energy physics i have 
understood that when particles are collided, they become a single 
particle where all kinetic energy is transformed to mass for a
brief instant. Someone explained that what we're doing today
is equivalent to colliding two pingpong balls (anti protons) to 
produce a bowling ball (a particle weighing approximately as much
as a gold atom). Now with accelerators being capable of 
accelerating particles to 99.9% of lightspeed is there anything
to wory about ?

Re: Can particle accellerators implode 'in our face' ?