I used to use those words quite often. Most of the time it was as a joke when one of my female friends would do something nice for me. I used it quiet alot when I was talking with my girlfriend (God I was so dumb back than).
Since there are many levels of love (love to parents, friends, teachers, siblings) I will concentrate on the love a man and a woman might express to each other. While all those types of love have a common factor to them we can safely agree that a love of a man to a woman is a unique relationship that is unlike anything else. When a man and a woman truly love each other, their relationship transcends the purely emotional plane and that love is also expressed physically (Having sex and having sex with someone you love are two completely different things, but that's going off-topic too much).
While we are at our youth we begin to discover love towards people who are not in our family, most of the time its a result of hormones rather than anything else; But, as we pass through relationships we begin to learn new things about love. I believe that at some points we begin to realize (most of us, anyway) that 'love' is not the thing we believed it to be in our youth. We waste those precious words by thoughtlessly throwing them at any person we like (like=/=love), providing not only those around us, but also ourselves, with false expressions of affection.
Today's American teenagers are the perfect example for my point: Boys and girls date for the sake of dating, not for love, they do it because its cool, they do it because everyone does it, but most of all they do it because it satisfies their sexual needs.
Lets review the main types of boy-girl relationships:
1. The Hook up - A boy meets a good looking girl, they hook up and break after few weeks/months
2. A common ground - A boy meets a girl who might or might not be good looking, they have something in common, they date for a period of several months/few years and break up.
3. The anime relationship - A boy and a girl are friends for a long time (childhood friends perhaps). At some point their friendship becomes quiet intimate and they fall for each other, living happily ever after. (This occurs mainly in animations and cheesy drama movies).
4. Love from first sight - Same as number 3 only that the two met not long ago and fallen for each other from first sight.
We can safely assume that number 1 occurs 90% of the time, while number 3 and 4 occur probably less than 2% of the times.
In my eyes true love is an endangered creature, that is rarely seen, and as we progress further into the 21st century, the younger generations are brainwashed with messages that encourage them to be promiscuous and seek relationships for the sake of sexual pleasure rather than love; From that we can assume that unless there is a turn in today's culture, true love will become even more rare, and we will be hearing 'I love you' everywhere, knowing that the person who said it probably just wants to get hooked up with the receiver of his 'affectionate' words.
For those reasons, and others I probably forgot to mention I have not used the words 'I love you' I almost a year now.
Since love is an emotion, a phenomenon which eluded even the wisest of men, and is something that cannot be explained by any logical mean. Every person has his own idea of what love means; Therefore arguing on this matter is really useless, all we can do is consider each other's opinions without trying to find the absolute truth.
Sorry for the long rant, this matter is a bit touchy...