Forget servos: they're just not strong enough for anything beyond the lightest of point-n-shoot still cameras.
That's a fairly odd statement, since servos are used in everything from BIG high-end CNC machines to, more saliently, camera control rigs.
There are all kinds of servos, not just those little hobby ones, but even a little hobby one can be brought to brunt with proper gearing. Notice a trick that servocity does with some of their pan and tilt mounts when using servos - they use the final drive shaft to run the servo potentiometer, allowing your control over the final shaft motion degree rather than the motor shaft motion degree.
I wrote about how to make your own servo using a DC motor a pot some time back, but you can easily attach your hobby servo to a geared-down final drive shaft.
I wouldn't discard servos because they're not powerful enough, but because they may not fit your application.
If you want to program it to move to certain positions, programmatically, you can achieve this fairly easily with servos.
If you only intend to do fly-by-wire, DC gear motors will generally be easier to deal with - there's no benefit of a servo in this case, except error correction (i.e. not moving as far as you intended to move). In fact, servos complicate the model a little.
Additionally, you could also do programmed positions by doing your own feedback loop (read: encoders) from DC gear motors.
You say security cameras, I presume you mean little tiny ones? What's the weight you're looking to move here?
Here're a couple of examples from servocity, the first being a full gimble-type setup to move a large camera, and the second, a smaller unit for moving tiny cameras. Their medium-duty units let you drive full-size dSLRs (I know, I've got one of their medium-sized units at home). They should help to give you some ideas on how to build one.
http://servocity.com/html/pt-2100_pan___tilt_system.html
http://servocity.com/html/spt200_pan___tilt_system.html
Let's not forget though, the great and powerful stepper motors =)
!c