I don't mind giving my number, and I have and have had any issues, but completing three debates is a bit much, especially when the quality of debates is pretty shabby so far from what I've seen. I agree it would allow more voters to participate though. Perhaps completing one debate would be sufficient.
I think having to give away your phone number, and complete three debates hinders alot of voting on user debates. I am not for giving out my phone number to websites, and I think completing three whole debates is too excessive. Plus trolls will find a way regardless of what requirements you put up. There are soooooo many debates I want to vote on, but I just cant see giving my number out to a website