Do you mean changing the just the name or the url?

I have changed the names on my blogs several times, and have not found any negative effects as a result of this. I have found that it may help my blogs search position that it they are been linked to under a veriaty of names.

I would not want to change to url of any of my blogs ever. I have been told it could be posible to change URLs without any negative effect but it is stil a risk that i don't feel happy taking.