In trademark law, the basic standard for infringement is "likelihood of consumer confusion." Just like famous people, however, famous trademarks are surrounded by additional security. If a trademark is famous, e.g. Louis Vuitton, Hermes, the trademark holder need not prove a likelihood of confusion, but only (under the new act) a likelihood of dilution.
This dilution may take the form of making the famous mark less distinctive because there are so many other similar marks out there (dilution by blurring) or harming the reputation of the famous mark by associating it with certain other goods (dilution by tarnishment).
The Trademark Dilution Revision Act in some ways makes life easier for the owners of famous marks, who now need only prove likelihood of dilution rather than actual dilution.