They engaged in a variety of activites including property destruction. By the way, not all members of the N30 black bloc were from Eugene Oregon. If you have more questions about anarchists at the Seattle protests, see our special FAQ . Over the past year there have been quite a few naive liberal calls for anarchists to take off their masks. In fact, there are many black bloc anarchists who don't wear masks during blocs.
Anarchists wear masks for many reasons.
The main one is the recognition that the police videotape activists and keep files on them. Masks promote anonymity and egalitarianism. They also protect the identities of those who want to engage in illegal acts and escape to fight another day. Tactics vary from black bloc to black bloc. Some common ones include unarresting and arm-linking .