While looking at bios on Twitter and on several blogs, I've noticed one common theme: everyone is an expert.
If you label yourself as an expert, you probably aren't. Any restaurant that claims "the best [insert food] in the world" does not have it. Self labeling is pointless and should be avoided. Your customers and consumers will do the labeling for you. They probably already are.
Do you or your company want to be industry leaders in social media? Then get involved. Interact. Put out quality content. Don't just simply join a few networks and then claim you are experts. You will be labeled an expert, when you show that you are an expert.
Two examples: Take a look at the bios of Chris Brogan and B.L. Ochman. Notice that you will not see the word 'expert' on their bio pages. Instead they give their credentials and site case studies that they have worked on.
The title of 'expert' is something that you earn, not something that you can self assign. If you are truly an expert, show it don't say it.