On my very first day as a non-believer, I told a group of close friends. When I explained why, most of them agreed with what I was saying, there and then. I was like, wow, that was easy! And all the arguments I've made since then, they've agreed with pretty much all of them. But still, they say they believe. They eat haraam food now, they don't pray, or read the qur'an, or go to the mosque.... but still they say that Allah exists. And it frustrated me for a while, because when I ask them why, they said just in case. But now it doesn't bother me, as long as they are not practising Islam, I don't care what they believe, let them have their comfort.
It's different with parents though, especially practising parents like mine, who could probably not even conceive Islam being false. The idea that your child is going to burn in hell for eternity is not a nice one for any parent, no matter how stupid it may appear to you. For that reason, I don't intend to tell my parents. Right now, they know I don't practise, and they leave me be, probably thinking that I will become 'straight' on my own. So I see no reason to tell them I'm not a Muslim any more. But if push comes to shove and they try to force Islam on me, as much as I care for them, I'm going to have to tell them. I'm not going to give up my freedom. Hopefully it won't have to come to that.
Prince Spinoza,
You sound like an interesting guy and I'm gradually picking up scraps of info about you from various threads.

So you live in Bradford? I'm assuming that's Bradistan means. And you have religious parents?
I live in Leicester and have very religious parents. As you will read in my intro thread, I have already come out to them about my apostasy and it went horribly. I agree with you that it is best not to tell them, if you can avoid it. If your parents know that you are not practising, and they are OK with it, you are lucky. If your parents are very controlling like mine were, I recommend you gradually try to get them to relinquish that control. When they realise that the control is slipping away, they will let go anyway. And you will never need to tell them. I started trying to get them to relinquish the control but it was far too late for them.
That is my honest advice, for what it's worth.

Sorry if this sounds patronising.
