As someone else already mentioned, this is not entirely false. You will lose your issues which is a huge reason why big projects don't move to Github. You lose your wikis. You don't run backup of your issues every day, do you? In fact, how many of you do that?
I bet the number is almost zero. Source code is one thing, but the history of discussion? That worth something.
Also, sometimes some repos just don't exist on your computer anymore or out of sync because you done work on multiple computers. Or if your computer is stolen.
I don't care about issues or wikis. I don't use either feature in the projects that originate from me (people send me issues but I don't use them to organize development). The code is the important part. Any discussion is already backed up in my email. And even if I did care about issues I could download them through the api, as was pointed out elsewhere.
I bet the number is almost zero. Source code is one thing, but the history of discussion? That worth something.
Also, sometimes some repos just don't exist on your computer anymore or out of sync because you done work on multiple computers. Or if your computer is stolen.