Why is my Launchpad missing app icons?

Sometimes my Launchpad just look like this without any app icons. What causes this problem and how can I solve it?

I am using 2011 11″ MacBook Air with OS X 10.9.1

This didn't work for me,
Finder did not respond, clicking on Apps gave this error

Could not obtain valid temporary directory for sandboxed app ...

I also had to open a terminal and run:

cd /var/folder
sudo rm -rf *

Searched for and opened Activity Monitor, stopped the com.apple.IconServicesAgent service and rebooted.

My icons came back in launchpad and dock.

A less intrusive way to tell LaunchPad to reset it's settings and regenerate app listing and icons is to perform this command line step:

defaults -currentHost write com.apple.dock ResetLaunchPad -bool true; killall Dock

Your screen desktop may blank and the dock will go away momentarily. If this doesn't work, the next step is to log out and back in. A reboot also could help further in some limited cases.

See more discussion at https://apple.stackexchange.com/a/194073/5472 and https://apple.stackexchange.com/a/150973/5472