Can I suspend / hang speakers?

The tweeters don't have to be at ear level; they can be angled downward so that they are pointing at ear level. I helped a friend install his home theatre and we hung a pair of Linn Tukan bookshelf moniters and a Linn Centrik from the ceiling using mounts from Good Guys. The Tukans are rear ported and sound great on the ceiling; just enough additional bass from the ceiling to give them a little more weight.

Just make sure the mounts you use are more than adequate for the speaker; ie, don't use one rated for 30 lb max for a 30lb speaker. Get a larger mount in that case; overkill it.

Sorry, I wasn't clear. He's talking a non-rigid mount, like with chain, rope, etc., that could be raised and lowered easily.

Non-rigid mount would be a bad idea, since the speakers would move in the opposite direction as the cones, according to Sir Issac Newton's First Law of Thermodynamics (at least I think it #1)- for each action there is an equal and opposite reaction. Only a little bit, but think how hard we try and make sure that speaker stands are rigid.

I did this in college when I lived in a storage room for a term (cheapest rent ever!) Hung 2 Boston Acoustics A60s from the rafters. Can't remember if they sounded good because I was drunk most the time. I doubt they did. There was a hardhat on the wall, in case anyone felt uncomfortable with it.

Yeah hanging from pipes mounted to the ceiling Joist would be sonically much better, all things considered(should strongly consider finding best sonic placement "in space first"). simply letting the speakers "hang" wouldn't sound so good, unless the speakers were "so heavy" they wouldn't react much to movement in the speaker.
I would "X" the hanging idea with chains, etc, yes. I mean, if the speaker is haning there anyway(obstructing walkways, etc), you might as well "hard mount" the suckers!