Absolutely yes. If you have an item of memorabilia personally signed with the intention of the item having value to anyone other than you, you have to be able to prove that it was signed by the actual person whose name is on the item of memorabilia. In other words, you need to prove it is not a forgery.
An impartial, credible, third-party witness can mean all the difference between an autographed item of memorabilia having value and being worthless.
See authentication for more info.