Here's what happened. Some close friends decided to go on a cruise. One of them did all the research and pricing and then upon agreement between the 3 couples, a booking was made with a major on-line booking company. 
Problems encountered were many. Client names were incorrect. Payments charged to the wrong credit card. Dining time arrangements were incorrect...but the most worrisome (understatement!) was the credit card billing that showed a charge to the arranger's credit card for a personal cell phone bill! The on-line travel agent had used the client's card to pay for his own phone bill!  We guess he hoped the charge would be missed and/or ignored! When confronted, he pleaded that it was an oversight, a simple error, and he would send a cheque to cover the "mistake"! The cheque arrived after some additional encouragement for it to come, and promptly bounced all over the place. A second cheque was received and the arranger had her husband immediately certify the cheque...just in case of course.  

After all these shenanigans, the travel agent still blithely acted as if nothing was wrong.

We wonder. How  often has he made such mistakes? Have others caught them, or has he developed a great system. After all, small charges are easily overlooked.

Then upon some further, after the fact, research, the arranger/client/traveller discovered that the cruise price should have been about $100 less per couple. Where did THAT money go?

All in all, a very strong warning message comes from this experience.

A) Book only with a person you know!  B)  Don't book complicated travel on-line C) Check ALL the details at least twice, BEFORE you travel! C) Double check ALL your credit card billings, especially after a major on-line purchase.

But, after 20 years in the travel business, a industry that has gone through major changes, especially with the Internet domination, I still would only book a complicated trip, like a cruise, through a face to face dealing with a real person. That way...you're covered by the industry travel fund/insurance, and you can actually see the person to have him/her help you with any problems before, during, or after the trip.  Book with an experienced travel agent...one experienced in the destination and type of travel you are taking.

If their is a service charge by the agent, smile, pay it, and consider it a very cheap form of insurance.

You can book simple airline flights on-line,  but for those special and hope-to-be-memorable trips...be safe and use a qualified, experienced and professional travel agent. You won't be sorry!