When manually adding leads it would be good to have the Source field available. Is this possible?

It seems to be a an error not to have it, as business is about people and we win a lot of work on recommendatiions (as I assume you do with your referral scheme) it would be good to havethis so that when we get a call and then add the lead in (with source) it is recorded an we can then assign the lead to one of our team.