Originally posted by: BOARD_of_command
Doesn't the laser have to hit something at the focal point for it to actually burn...? Think of burning CD's for example. It's strong enough to penetrate the plastic and gouge the actual disk, but it doesn't melt the plastic because it's only focused at the point of contact with the actual disk. I've used a very strong laser before and no matter where I placed my hand, I couldn't feel anything.

It damages the eye not because it's hot, but because it's so bright that it damages the sensory nerves inside your eye. Am I wrong about this whole focal point thing?
Focal point is kindof a relative term. Some light sources, or sources in combination with lenses have a minimum focal point. That is, there is a spot size that is the smallest possible, you can't reduce it down to zero. If you have a perfectly collimated beam, it will have a focal point of infinity since the rays will never converge. In general, laser pointers try for this perfect collimation, but in actuality are slightly diverging. This is why your laser pointer beam gets larger and fuzzier at greater distances. Now, you can use a lens to focus the beam. What this does is it increases the power per unit area. Five milliwatts over a 1cm radius isn't going to do very much, but once you have five milliwatts concentrated to a spot of half a millimetre radius that spot starts to heat up. You're delivering more power to it than it can dissipate, and it absorbs this power and starts to burn (speaking of a generic flammable material of course....every material will have a different heat capacity, rate of heat dissipation and rate of absorption of photons, etc.). So you could be using a 10 Watt laser, but if the beam is really large, it won't do much more than a tiny laser pointer.

For these lasers advertised, they would need to be held for a while on a single spot to make it burn. The rate of heat absorption needs to be greater than the rate of heat dissipation, and this ratio will determine how fast your material will heat up.

And from what the webpage says, it seems as though the buyers of these lasers want them mostly for commercial or industrial applications as tools or aids in experiments. They specifically caution against using them as laser pointers.