The custom in many continental European countries is to kiss each other in greeting. This seems to become more prevalent and the kisses more numerous the further south you travel.
In Amsterdam, I didn't see anyone greeting each other with kisses in public, but I do know that it is customary to greet close friends with three cheek kisses (left, right, left).
In France, one always kisses hello and goodbye, or good morning and good night. In Paris, the custom seems to be two kisses (one on each cheek) and might increase with the closeness of your relationship to that person. On Ile d'Yeu, the custom is four kisses, no matter if you just met the person or have known them your whole life. Public displays of affection seem to be rampant in Rome.
The day after I fell off the bicycle (see post titled, "It's like riding a bike?"), Jacqueline fell on some stairs and smashed her chin and cheek. It hurt when people kissed her on the cheek so I introduced the L.A.-style "air kiss" to accomodate her injuries. The family thought that was amusing.