It sounds like a really good gossip magazine, doesn't it? If you're like me, you've experienced it with kids, whether your own or in the classroom--kids who have the NEED to tell you what somebody else is doing.
Kids tattle for lots of different reasons. It's been my experience that most young children "tattle" because of their developmental stage. Morally, they're very bound to rules, and everything is black and white. They look to adults as rule enforcers, so when something goes wrong some kids are going to feel the need to inform adults. It's a way to feel stable and secure. You know, just in case it got past you, I'm letting you know that Jordan took that other block. Children at this age are still distinguishing the difference between tattling and getting help when it's needed as well.
I think often we assume kids are "tattling" for attention or for the opportunity to get another person into trouble. As some children get older, this may happen, but it doesn't always, and it sells our relationships with kids short to post blame for something that is developmentally typical. So the question then becomes one of teaching children what's necessary to tell about and what isn't. Generally, a good rule of thumb is to guide kids to "tell" about things that might hurt themselves or somebody else. As children start having to evaluate actions of others, it causes them to think critically and redefine what requires adult intervention. This encourages children's autonomy and self-regulation.
Some kids don't pick up on this idea too easily or really feel the need to continue to tell adults things that they don't need to know or don't need to be involved in. For these children, I'm a believer in setting some boundaries around when and how "reporting" (tattling) takes place. One of the things I've found particularly helpful is giving kids a place to "write" about what it is they need to tell me. Even children who are not yet writing can participate in this by drawing their ideas or "writing" to themselves. The key here is to set up a time of day where the child or children can report whatever it is they need to say. Whether you promise older kids you'll read through their notes or younger kids the opportunity to tell you whatever bothered them, that time for reporting is critical because it reinforces the idea that you take their concerns seriously. It also provides a "teachable moment" for you to explain the difference between telling you things that are critical and telling you informational items that don't really affect anyone.
Helping kids differentiate between true tattling behavior and asking for help to solve problems beyond their control is a responsibility adults need to embrace. The end result of stronger critical thinking and problem solving skills, as well as greater social skills, make it worth the investment of time.