Can I safely remove old versions of Xcode which are using a lot of space?
Yes.
If I can, what should I do?
Run:
sudo <Xcode>/Library/uninstall-devtools --mode=all
Where <Xcode> is usually /Developer but can sometimes be ~/Developer depending on whether you installed it with sudo privileges or not.
Once you've run that script you can just move /Developer or ~/Developer to the trash, you don't need it any more.
You can can get more details about uninstalling by reading the About Xcode.pdf document in your directory.
If you also have a /Developer-old directory you can just move that to the trash.
I'm having the same issue. At first I thought it was me doing something wrong, then it hit me again last night.
I am using a corporate macbook pro I7 (which seems to run slower than my personal 2009 macbook core-2 duo, but i regress...) I was vpn'd into work with Cisco Any connect.
I got to a stopping point, went to commit the files, added my comment and before I hit the commit button, I lost the vpn. No problem I thought as the commit is only to the local repository, but when I hit commit, I got an error saying this is not a git repository. I flipped back to my project and half the files were gone. Luckily the 4 files I had been working in were still there, but I had another project open at the same time, and I lost everything there but the project file. Luckily I had pushed to our git server twice that day, but did lose a little work.
The computer is running McAffee AV.
I'm wondering if it's something to do with the mobile account on the mac.
None of the source code files are in the trash, they just vanish.
I'm storing my projects in ~/Projects/Mobile/Project1... but I have also lost source code in ~/Documents/Projects before.
Zip files in the ~/Projects/Mobile folder are unaffected.
All source code files in MOST all project folders disappear, even projects that were not open in XCode.
Best Answer
You cannot deselect them. As apple mentions here they are automatically added to explicit app ids. The only way to do not have them is to create a wildcard app id (which is not a solution in most cases as it has many drawbacks).
Think of them as libraries added to your app. You do not have to use them and they change nothing to your project or to the way your app appears in the app store (unless you use them of course).