A con to student services hours are it would go from volunteering to being forced to do it so students would not actually feel motivated to help. With that students will actually not be benefiting the community just hours showing that they were there and the people who actually volunteer have to do more lifting to make up for the others. (http://silverchips.mbhs.edu/story/10799) With that it really takes away the meaning of volunteering and it would feel more like an unpaid job of communist North Korea rather than helping the community.
I think having mandatory services hours really is not good for everyone. So, most students cannot will not actually have motivation to volunteer like myself, unless it was in a disaster or someone needed help. Also, it looks better to colleges showing you volunteered without having to be forced to do it, giving you a better chance of being accepted. So, it is important that we keep mandatory service hours out of school and allow students to decide if they want to or not.