There may be fake sites of which people are not aware. Some sites ask users to enter their personal details such as PIN numbers. It is dangerous to enter this type of things. They charge extra 5% money than usual.
2 2 2

This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
1.  There is a danger of on line frauds on the payment sites.  We have to be careful with the security and protection of our ATM, credit and debit cards related information.

2.  We do not receive the refunds immediately.

3.  Every one does not have computers to do reservations.  One needs to have internet facility.  It costs.

4.  Often the responses are slow from the reservation/ticketing server machine.

5.  The company takes care of the data security for the online data of all users.
  So the company is to be trusted.

6.   There is a commission for reservation and also it costs to print a e ticket on paper.

7.   Some times when we want to change our travelling plans at short notice, the cancellations and re-bookings can be difficult to manage.