In short, we want to make sure that everyone gets a fair chance to buy tickets – the limit's there to keep the first person in the queue from buying up all the best seats and leaving nothing for the everyone behind them!
The ticket limit will usually be decided by the event organisers and we'll make sure we advertise this at the very beginning of the booking process on our website. It usually applies per person, per credit card – sometimes, if it's expected to be really popular it may also be per household. Please be sure to look out for this – you can't book more than the limit in any one transaction, but unfortunately, we can't stop you from going in and making a second booking.
It's not that easy to get around the system, though – if we do find that someone's booked more tickets than they're allowed, we may well cancel some or all of their tickets, without notice.