There is truth to that. In addition to the "influence" reason for investing, there is also just regular speculative investing - hoping the price will continue to go up (or at least not go down at a rate faster than the SP interest rate gives out). There does need to be a buyer for every seller though, and at some point the price will become high enough that the risk vs. reward will not encourage more speculative investors to buy back in. Then it will go back to needing more "influence" type buyers.