A Michael Jackson autograph is in high demand due to his recent and tragic death this year.
This perfectly illustrates the impact on the value of an autograph if a person dies. A signed picture prior to his death could be had for around $150 with excellent authentication sources, and I've seen that price easily double or triple in some cases since his death.
If you look at the incredible demand still for Elvis Presley and Marylin Monroe memorabilia, for instance, and you can assume Michael Jackson will continue to be in demand for a long time.
Jackson was known to be a relatively good signer, but obviously the demand far outweighed his ability to sign for everyone. Jackson was very reclusive and there just aren't that many of his autographs available compared to other celebrities.
I saw Michael Jackson at the Forum Shops in Las Vegas in 2001. The frenzy of people trying to catch a glimpse of him was incredible. I tried to get him to sign a receipt (all I had on me at the time!)but he signed for the person next to me.
Examples of his signature and Michael Jackson memorabilia are on this page below. As with buying autographs in general - buyer beware. The recent interest in Jackson has caused renewed demand for his autographs.
If you are looking to buy one, be sure you are dealing with a reputable source. It's hard to say from an investment perspective whether the value will continue to increase over time, or possibly has spiked and will remain level.
Personally I wouldn't even consider buying without
authentication
from a reputable dealer, or obtain third-party authentication from a source such as
PSA/DNA
or
James Spence.