Who is a knowledgeable Employee?

The knowledge for any employee cannot be determine based on Job Hops or single Stint.

But the employee who has job hops have more knowledge, because everywhere he/shw get new learning it may be functionaly, technicallt etc...so that employee has more domain to work. It is not always fix that an employee is working in a company form long time have good knowledge of all domain, He may be expert in specific domain in whihc he/she working.

New Skills and Attitudes to Unlock the Intellectual Capital in Your organization

I see THREE basics reasons that candidate look to HOP.
1) They see some other company paying high salaries OR his/her friends studied with him /her making more money than him / her.
2) Not comfort with the people around.
3) Over loaded

1st case - candidate has to think about the basic ethics.
2nd case - candidate has to speak to the manager and try to solve the issue.
3rd case - if you have hands full of work, you are the most luckiest person in the world, Are you really over loaded? you have to speak to the manager and try to fix it.

Job hopes will give more knowledge. Today if a person is sticking to a same company he seem to have less knowledge of various industries...... Today having a deep knowledge in one subject will not help, companies are expecting people who can do multi tasking and smart....  

The Job Hob will have excellent experience in having seen the various successes and failures of organizations, the ifs and but's, as well as, how not to run a business.  This invariably makes him in a better position than the one who has a Single Stint in a single company.  Also, the Single Stint man will be afraid to come out of his known paradise and his willingness to take risks will be very less.