Twitter is now showing a sample of matching usernames/accounts for name-based queries on Twitter.com. A search for [bill gates] (without @ symbol) now shows Bill Gates account and the names of two others above the tweets that match the search query. There's also a link on top right to View all name search results. Note: If you've a VIP account "You'll see a "sign next to the name", otherwise there's no indication, about the authenticity of the account."
If you're a celebrity, this should mean a big increase in followers who can now find your account more quickly. But, as TechCrunch rightly points out, this name-based search will also surface many fake accounts that trade on the name of celebrities and other well-known figures.