Jewish Business Ethics: Halakhot of Investing in the stock market
from jewishvirtuallibrary.org by Rabbi Asher Meir
I. THE NATURE OF STOCK OWNERSHIP
The extent to which stock ownership is considered active partnership in a corporation is a critical question in numerous areas of halakha. Conceivably, by buying a single share of stock a person could find himself committing transgressions from all four sections of the Shulchan Arukh! Some examples include: