How to hang a mosquito net safely over a bed?
Use coaxial cable clips.  Don't screw the flap side in.  Also the part that you screw in, leave a small gap so that you can tuck a little of the flap side in.  

I have two cable lines in my basement laundry room that I switch (don't ask).  It holds the cable great which is heavier than a mosquito net and with a good tug my cable is on the ground.  Of course this will work better if you screw into wood and if you aren't then you want to use some sort of anchor.  You can play with the "tug rate" needed for collapse by how much you tuck in and how tight it is.  Really with a mosquito net this could be very loose.  And the small screw holes can be easily concealed after.