Discourage somebody from taking up the LEGO hobby?

A some what strange question, would you ever "discourage" somebody from taking up the LEGO hobby?

Background: At work we have somebody who has a habit of jumping on to what other people are doing. In the past when somebody was talking about fishing he went and purchased a heap of fishing gear to also do it. A few months ago he found out somebody has a collection of guns and now he wants to get in to this too. He gets obsessed with things and does not leave the people above alone now he thinks they are his "friend". His manager has had multiple talks with him about this in the past.

I am on leave at the moment but have heard that he is keen to talk to me about LEGO and getting in to it when I return from leave.

Sounds like he needs help, though we all know Lego is good for the mind.....stops me from going crazy. 
It's that it's a person's choice if they wish to over do themselves on a theme of the month, you can only suggest him not to go crazy buy, buy, buying everything.....hook him on one theme as long it's not your favourite theme so he doesn't drive you crazy.

Thanks for the reply. He has already decided that he wants to get in to my theme (Technic) and I have heard he has a list of questions for me when I get back

I will see what happens and if I can steer him in the right direction.

You might need to tell a white lie and let him know you are getting bored with Lego and looking at doing other hobbies, hobbies you haven't decided on yet.