Not being allowed to take a bike at all on the Waterloo & City Line makes sense, (not that anyone can do much on the Waterloo & City Line at the moment anyway), but why no bikes at all on the DLR? I'm positive that I have seen people with bikes on it, so is that only a fairly recent rule?
The Victoria Line is entirely underground, so I imagine that might be the reason why you can't take bikes on it, but how come you can use bikes on the sub surface section that of the District Line? Is it anything to do with the depth of the stations there?
Is the rule of not carrying bikes in peak hours due to the amount of space they take up or for some other reason? If it's a space issue, why then are people allowed to carry enormous suitcases the size of small camper vans? Or large rucksacks? Particularly the people who seem to forget they have a rucksack on their back and insist on pirouetting through the carriage, knocking over people who unfortunate enough to be standing behind them.