Yes, there is a risk of companies exploiting geoengineering as there is a risk of companies exploiting pretty much anything. Companies must always look out for the bottom line, money, and one of the best ways to garner money is to exploit whatever process a company can. Thus companies may exploit geoengineering.
Geoengineering is always risky because we do not always know what will happen when we use the earth for our own purposes. Climate changes are not something that can easily be linked with man-made changes because there are so man variables involved in temperature and weather patterns. Geothermal energy could be a viable source of renewable energy but may have drawbacks we do not understand.