domain driven design - DDD: SO tag. An Entity or value type?

Question

In the context of Domain Driven Design, is a StackOverflow tag (ie. ddd ) a value object or entity?

EDIT:

Imagine, that you have to build SO website. How would you consider 'tag'?

Answer 1

To expand a little on awhite's answer a tag is a value type Why? Because it doesn't make sense to have

var tag1 = new Tag("DDD");
var tag2 = new Tag("DDD");
Assert.AreNotEqual(tag1, tag2);

clearly they should be equal to each other because a tag has no identity except for its label. Questions and answers on the other hand are definitely entities