People who arrange dates online are "savvy shoppers" who blow their top if their date turns out to be different from the way they advertised themselves on the web.
This is one of the main findings of research into online dating by Monica Whitty, a specialist in cyber-psychology at Queen's University Belfast.
Dr Whitty, who presented her findings in a keynote address at the annual Congress of Psychology Students in Ireland last weekend, said: "They've put time, energy and money into this, and they're not going to waste time on someone who doesn't match up when there are so many others."
Some daters appear very picky. One female dater was "incensed" to discover her date was just one inch shorter than he had claimed.
Others appear to have genuine grounds for complaint, such as the woman who found her date to be short, fat and balding, and nothing like the attractive photograph he had posted online.
"He explained: 'That's my brother, and I thought I looked pretty similar'," Dr Whitty said.
Women were also prone to stretching the truth, generally lying about their weight.
One defended her description by saying: "Average is a little bit overweight, isn't it?"
A number of daters posted photographs of themselves at a younger age, claiming they had no decent contemporary shots.
But Dr Whitty found that many made an effort to be as honest as possible, even changing profiles following complaints from dates.
Many also sought help from friends and family in constructing their profile, to make sure that they were presenting their true self rather than the person they thought they were.
Dr Whitty found that on major reputable sites, the average age for female online daters is 35, and for men it is 40.
Reasons for going online ranged from finding offline choices limited to getting tired of the pub and club scene and working shifts. Few of the daters were confident about using technology, and saw online dating leading as quickly as possible to an actual date rather than the start of an online romance.