Of course you can. Like everything else – from posting pictures of your vacation to “What Kind of Tea Cup Would I Be” memes, “vote for me” pleas can reach a point of annoying people.
You know your friends list better than I do. When you reach that point you are going to have to decide what to do from there.
After all, it’s YOUR LJ. If you want the people who signed up to be a part of your friends list to read your entries – you know, things about YOUR LIFE – and want them to support you, there is absolutely nothing wrong with that.