I have written about dating a lot. Here I go, again:
Dating by its very nature and purpose is about finding Mr./Ms. Right and to do this means that we go out with lots of people in order to learn what humanity has to offer. Doing so makes it easier to determine when this person comes along, and, it develops recognition skills that help us determine what we like and do not like in a person, and what qualities are valuable. By dating lots of people (even at the same time) we expose ourselves to lots of likes, dislikes, quirks, interests, morals, values, goals, mannerisms, ideals, etc., et cetera, etc.
Dating is not all about stopping with the first warm body who comes along expressing an interest in us. It is not all about being exclusive with each other to the exclusion of all others--at least not until a long time later. Dating is about becoming closer to a person than is possible thru a casual friendship. By becoming "closer" you are then able to learn more about each other.
There should be no exclusivity until you and the other person are ready to settle down and marry. Until then, you can be kept busy with the relationship(s) you have with one or more people. Exclusivity with one person is not a guarantee that you will always have a date or be kept socially busy. By not being "exclusive", particularly during the teen years, eliminates much of the angst, drama, and trauma in relationships that a teen is not yet prepared to handle. The same can hold true for adults even though they should have matured having also developed better interpersonal coping skills.
By dating more than one person and at a time, you stand a much better chance of filling your social calendar, learning new things, and as noted above--exposing yourself to a variety of personalities that will help you determine when Mr. Right comes along.
Because dating by its very design is not and should not be exclusive, and there is no legal contract, there can be no "cheating". If when the time comes that you want exclusivity, then it is often implied long before by simply behaving toward one another like it is or has been. Your behaviors toward each other tell the tale. Until such time both people are free to date others should they choose. Until such time, devote lots of your dating activities deciding whether this person is marriage material, worthy of exclusivity, and only when you are ready to work on this aspect of your life make this commitment with each other.
If you want to meet that "one in a million" guy or gal, you have to date a million people.
For additional insight and information with regard to internet friendships, please read this article:
"Dating" and the Internet