Re: Earning the spread...

On very rare occasions, when LP's get out of sync, you will get a positive spread (Ask dipping below Bid), but there's no way that any retail trader is going to earn enough to make a living from it.

Re: On average there is a trade every 1/2 minute...

You might want to have a squizz at this...
http://www.youtube.com/watch?v=B_k_elbBz8c