Sometimes , I feel like we invest domain name is just like a gambling .

We don't know which domain will give us the return. Maybe we invest a lot of money for a domain , but at last we may find there is no return or no any profite. And also, when we invest a little money , but finally , we have make a big money.It is so like a gambling, we all know what will happen in the future.

Yes you are right! But if you have futuristic mind it will be great.

I know in Canada lives the guy that have the largest domain name list. I feel he is not going to sell all of them in the near future

When i buy domains I calculate if I can get a return on my investment within 2 months. If I can then as gambles go its not a bad one.

I guess it depends how you value your domains, how you monetize them and how much you "invest" :-)