Originally Posted by
UKtravelbear
It takes a couple of minutes (if that) to set up an account with TFL.
Any erroneous charges (such as incomplete journey charges) can generally be resolved on-line with no need to speak to anyone at TFL.
I can't see anything on the TFL website about not having multiple cards on the same device but I don't think it's a good idea simply due to the ease of making a mistake and over paying as well as the hassle factor of switching between cards on entry and exit and delaying other people!
+1 on the delaying other people. There is a marked delay in gates opening when using a phone app compared to using an Oyster card. If you're going through a major West End station at peak hour you're likely to get people walking into you and your group because they won't be expecting one person to tap a device, let someone in, change cards, tap again etc. The crowds can get pretty big at times at anytime of the day or night.