Yes you can just cut and paste.
I don't know about in iPhoto, but in Finder, iCal and other apps, if you hold down option while you drag 'n drop it will copy. I would assume it works in iPhoto as well.I've never copied so dunno about that... but yeah, I would drag the photo out of one event onto desktop import that photo back into iphoto, then repeat the Moving procedure.... if there's an easier way to "copy" someone please tell...