Whether it is for financial gain or personal enjoyment, I have invested in wine.
Personally, even outside of monetary gains (or losses!), I believe that anyone who purchases wine to lay down for a period of time before enjoying it is purchasing wine as an investment. You are buying wine at a set release price to then 'incubate' it for a period of time to receive additional pleasure from bottle age under ideal storage conditions. It is also an additional investment to maintain those storage conditions and 'lease' space for bottles until they are ready. That aged bottle that you can enjoy or sell may cost considerably more than the bottle did at release. Or at least you hope so.