Eh. Forced teleports were probably a bad idea. I personally would probably allow it to move folks to unsafe spaces that a slide could move them to. And allow the same save a slide would allow.
Why? Because as I read it, a forced teleport is just a fancy slide.
How do you read it that way? Slide is movement through squares. A teleport completely bypasses those squares. They're two entirely different mechanics. If you try to teleport a dwarf, will you teleport him less spaces due to his racial abilities and any feats he might have to resist forced movement? NO - that would be ridiculous.
I'm constantly amazed how people can go out of their way to make straightforward rules all convoluted.
People can rule that for some unknown cosmic reason (otherwise known as DM fiat) you can't teleport enemies into dangerous squares, but these are house rules. No such limit exists in the PHB... and if a DM planned an encounter next to a 30 foot pit not realizing his Spellstorm Mage player could teleport all enemies in a burst 10? Whose fault is that?