One could take it further and allow shareholders voting power over the individual's actions, such as their vote in elections, or where they will move to. For example, you may want to move to a pleasant neighbourhood, but your shareholders may prefer you to live somewhere cheaper, closer to work or otherwise more profitable, and until you buy back majority ownership of yourself, you don't get a choice. Putting your career on hold to raise a family may also be out of the question until you have majority ownership of your personal stock; if adverse economic conditions kept a lot of poorer/less successful people from buying back their stock before their biological clocks run out, some social-darwinists may see that as a good thing.
Of course, there's the matter of the whole scenario looking a bit like slavery in neo-liberal-capitalist garb, But still, it could make for a good fictional scenario; or possibly the kernel of a Swiftian essay.