The above poster is incorrect.
When I started dating Jordan, we weren't exclusive, meaning we weren't "boyfriend/girlfriend". And we did have to have the talk, because I personally started to become confused about our status and where we were headed at the time. Sometimes, people just need clarity, and that's ok.
We had the talk about a month in. And in our case, at the time my now-fiance said he wasn't quite ready to start being exclusive with me. Did our feelings change? Absolutely not. And it was actually only shortly after that we -did- become exclusive.
Basically, if you're talking about a non-exclusive dating relationship or a close friendship where you're looking to start talking about taking things to a more exclusive level, there is no wrong time to have the talk. "The talk" is just about expressing your true feelings to the other. By talking about it, it shouldn't "change" anyone's feelings or scare them. It should make them confident that you are an open and honest person.
However you do have to be prepared that the other person may not be ready (I was fairly prepared, because I knew my fiance had relationship apprehension at the time), and remember not to take this as a necessarily negative sign. It certainly wasn't in our case.
Remember that it's less about giving a speach, it's not about convincing them to be with you and only you, it's just about expressing your feelings and seeing if they feel the same.
~ Lynn