You can’t directly export paths to Illustrator, but Blender 2.73 can export Freestyle lines to SVG format. Turn on Freestyle in the Render panel, then tik the Freestyle SVG export box below that. You’ll have to play around with the Freestyle settings to get what you want but it works very well. There is another Export SVG plugin floating around but I can’t find that one at the moment.
I’ve use Freestyle for some technical manual-ish illustrations, and once or twice I’ve enabled the Freestyle SVG export and looked over the results. Occasionally, they proved really helpful. For example, in still scenes of a computer desk and the stuff on top of it, I was able to bring in the SVG lines, which aligned perfectly with the rendered drawing, and use those SVG lines to fix or change a few corners or small details.
I usually leave that option unchecked, though, because sometimes, I’d forget it was on and I’d render a Freestyle animation, and later I’d find it had spent a lot of time updating a huge SVG file of each frame rendered. I haven’t really looked at those huge files much.