Can I use SMF as a dating website? Can you show me a sample?
Well SMF is a forum. You are free to use it in anyway that you want. I am not sure how much customization would need to be done to meet your needs however. Perhaps none if you wanted it to be basically a forum where people can meet each other.
As for a sample, do you mean an example of a dating website that is powered by SMF? I am not aware of one myself but you can try searching using a search engine to see if you can dig up anything.
If you are after a demo SMF forum, there is this - http://support.simplemachines.org/demo/