In various places you will find hints that security people really don’t like people to use public PCs in places like cyber cafés, etc. It turns out that this is not just a theoretical risk, but a genuine threat that has been seen for real.
Krebs on Security has a report indicating that not only are key loggers in use around public PCs in hotels, but that they are common enough that it is worth making special mention of them.
Whilst very convenient, whenever you use a public PC under the control of a third party, you never have full assurance that the PC is behaving properly and not stealing all your personal details.