Frankly, what do you think of a manager who is spying on his staff on Bayt, LinkedIn, etc ... In order to predict their behavior and departure of any of his members?

Frankly... he has as much right to safeguard his interests as everyone has to search for better opportunities. However this might be a sign that he knows that he hasn't been providing fair treatment/package to his team members and suspects them to leave.

Providing team members such working environment which they would not leave even when wooed is a better approach in my view.

I don't know why you consider it as spying! from the beginning its your choice to set the privacy.

Let me turn the question back to you: How do you feel and what are you going to do if you coincidentally found an advertise from your company about your job as a vacant? I believe you would think that you are not good enough and you'll try to do something positive to keep your job, and you are going to check with your manager for whats missing.

Now you know that your manager is care of you and he checking about your satisfaction.   

this is a crazy manager and not professional

As the Professional Said the Good Manger have NO need for spying on his stuff , because it is a personal privacy and each one of the team if he leave the work shouldn't affect the work if all work have perfect documentation

Also some companies make condition to give exchange or training the new engineer for one or two months  

the contract save the employers & employees rights so why any one make spy on social media or from his colleges ?  

A manager has enough work related direct contact with his staffs in day to day activities, meetings, and also in informal gathering.  But then so what? A staff has the right to a career move, and same is the case with manager also. As long as the staff is delivering results for which he is paid for that should be fine and as per his contractual right, he/she may quit the job after observing necessary formalities. This is one part of question

 Secondly, it is not wrong to interact with social media like Bayt or linked-in after office hours. These social media certainly help someone to build up his CV, see his/her strengths and weaknesses, and acquire the required skills for the changing job market. This approach is good for everybody, even for the current manager or employer.  

 So, I do not think, the manager is really interested on spying on his staffs through social media. Again, I would recommend, no one should put false information on social media website or make abusive comments. It should be a place for free-flowing information

 Let us this utilize this technological breakthrough of social media to make this world, a more livable place.

Thanks for the invitation

Agree with my colleagues

I don’t  have need and even time for spying my his stuff. If someone is going that way probably he/she is not real manager but is Search for wine and looks for excuse to hold someone for its widespread ignorance deficiencies competence therefore spying other. Sometimes the same employer requires such behavior from the manager but it is only a not too well testifies to the employer. Lack of confidence is one of the reasons for the failure of the projects.

Well the term spying itself is not worthy of a good manager. A good manager is always a great leader. He knows about his team without even thinking about spying. He can really inspire them to continue with the organization through his leadership and even with giving them full authority to have their career rights. He is the charismatic boss I would say.

this mean he is not professional manger and he doesn't trust his crew 

Agree with Mr. ahmed khater  view

To do this means that he doesn't trust his employs. But also the employs doesn't feel confident with their leader.