According to Facebook, if you send a message to a company, they then have permission to send you sponsored messages—or as we humans call them, ads. These will be unprompted “highly targeted, in-context” ads. Businesses that already have chat bots set up can start using the new feature immediately.

Source: Facebook Will Let Brands Send You Ads If You’ve Messaged Them Before

It seems to me a good reason to not use Facebook to get in touch with a company