06-11-09: Onhwy61Don't count on that. The Mirage M5si from the mid-'90s is 51" tall and 85 lbs. each. About 6 months after I got a pair, my then-5-yr-old was playing with the dog and managed to knock one over and break the fastener that secured the endcap to the column. Nobody got hurt. I was away at work and my then-wife and son kept quiet about it until I discovered it on my own weeks later.
Kid-friendly is different than kid-proof. I'd recommend any floor standing speaker with a large footprint (can't be knocked over).
As mentioned, the large footprint would have helped. The M5si base is about 16" wide, but only about 8" deep, which is the direction it fell over. You can also buy aftermarket outriggers (e.g., Soundocity) to provide a more stable base for almost any floorstanding speaker.

