Yup, it is!
The idea is that whenever you see a site that has the National De-Lurking Week button up, you will HAVE TO leave a comment. It encourages all lurkers of blogsites to stop lurking and starting dropping a line to say hello! It's time to get out of the closet and speak up! Why? It's the rule, and we hate breaking the rules, don't we? :-P
So stop by, read, then say hello! :-)