What industries do you regard as being highly competitive? can you identify any barriers to entry in those industries?

Five Industries as being highly competitive and their barriers to entry.Farming and farm supplies —  the barriers are the cost of land and machinery or in the case  of chemical applications, licensing. 
Consumer electronics – the barriers are brand loyalty or control of essential factors of  production.  Dry cleaners – Barriers are the availability of suitable locations (near residential areas  and properly zoned) and the availability of equipment, in addition to high start-up costs.  
Internet Service Providers – the barriers of the internet service providers are the knowledge of running a server,  cost of a dedicated trunk line for access to the telephone network and the cost of purchasing a computer server.
Taxi service – the barriers include the need for taxi medallions, which must be acquired through an expensive legal proceeding or purchased from existing companies.