Well Loaded Dog summed up the other side of experience pretty neatly.
Every person rides a bike differantly, braking at differant times, leaning differantly, changing gear at a certain pedal speed.
Even an experienced rider will take time to develop confidence and they may well try to lean the machine over when the front man does not want it.
The trust can take a long time to develop, and working together is a skill that has to be learned. Communication is important.
I’ve seen two lads on a tandem who were so mentally connected that they could even climb away from good solo riders, and tandems are usually notoriously slow uphill.
I’d say that balance is necessary, a good tandem team can learn to lean together and not upset the handling.
The best way to prove balance in this respect is to be able to ride a machine solo.
I have seen tandems with conversion kits that allow one parent to do the driving and one of their children to sit on the back and kake their contribution via an extra set of pedals affixed to their seat tube. Some of those children possibly cannot ride solo.
If you are a cyclist and you are ever in the UK you absolutely must go to the Cyclists Touring Club(CTC) rally in York sometime in June - you’ll find links on the net, here is one for you.
http://www.amkirby.demon.co.uk/NYDA/YorkRal.htm
You will see more odd bikes, trikes, tandems, tandem trikes, triplets, maybe even a 4 seater than you will see anywhere else and all being used.
If you are interested then e-mail me and I’ll dig up more info and maybe act as your guide for the weekend.