Interesting piece from the Hong Kong Standard - German Intelligence agencies have warned that Chinese spies are impersonating search consultants on LinkedIn.  At least 10,000 German citizens have been contacted, according to the BfV, and it is reasonable to assume that other nationalities will also be at risk.

Very cloak and dagger.  That said, I suspect most executives on LinkedIn are more concerned about being monitored by colleagues, clients and other work associates.