A few classes down the line from the start of this thread, I've been subconsciously considering this 'jamming' thing in my own practise..
I think some folk consider that I may be jamming them when they:
a) Initially take my balance then put me back onto a strong posture through thier next movements
b) Try to move me in a direction where I am already in a strong posture (ie my skeleton and muscles are in good alignment, and moving me in that direction is going to be hard work, even through I'm not all that big or strong)
c) Simply don't take my balance at all and leave me standing upright on my feet (again in good posture)
Some tori appreciate my honesty, some don't understand why 'it's not working' although I do always explain eg 'You didn't take my balance, try to enter or turn further' or 'You are going through my strongest line, this is where I am weak, try moving that way'.
I could just fall over for them (taking my own balance) which I will do with complete novices who are only managing an approximation of the technique because it's their second class, ever
but do not see the value to tori if I do so for somebody who has been training for 6 months or more..
At this stage in my development, if uke's balance isn't broken, it isn't Aikido