They can be if you do not pay them back on time!
Payday loans are meant to be very short terms loans for only a few weeks, that are then re-payed at your next payday.
If they are not paid back on time or need to roll them on for another month, some have very high charges, and this is what has given them a bad name.
If you are thinking of a payday loan, be sure that you can afford to pay back as planned in a few weeks.