Recently I posted regarding Prayer Partners for SRC, and a commentor asked why the deliniation "Out Loud". The answer kept getting longer and longer, so I never published it. Let me sum up.
1. Jesus said, "if we don't praise, the rocks would cry out"(BRV)
2. God created us oral beings who articulate through speech more than any other creature in creation.
3. When God baptizes us in the Holy Spirit, He gives us a physical evidence...Speaking in tongues.
4. Jesus prayers and every other prayer in the Bible is recorded because they were spoken out loud.

Ultimately though it comes down to knowing myself. In college I found that when I would go to the cafeteria and "pray" over my meal, I would just drop my head and silently "pray". The problem was that I wasn't really doing anything but dropping my head. There was no prayer, no thought of God whatsoever. I realized it one day and realized that for my sake I had better change my prayer strategy.

Not every thought is a prayer, and I've heard many prayers which could've used a bit more thought, but bottom-line... I find praying by name out loud makes me live up to the petitioning part of prayer from Philipians 4. That's why I do it, and ask others to.

--Ben