Well, the OED gives several possibilities. If one is 'frogging', one is 'catching frogs, fishing for frogs'. One might 'frog' a coat - that is, apply 'frogs' ('An attachment to the waist-belt in which a sword or bayonet or hatchet may be carried.' or 'An ornamental fastening for the front of a military coat or cloak, consisting of a spindle-shaped button, covered with silk or other material, which passes through a loop on the opposite side of the garment.'). And so on.
That it's actually a verb surprises me. I was just intending it to be a pun on the game Frogger. I thought, "one who runs is a runner, so what does Frogger mean?"
Some research says that lurkers make up over 90% of online groups. I suspect that Less Wrong has an even higher percentage of lurkers than other online communities.
Please post a comment in this thread saying "Hi." You can say more if you want, but just posting "Hi" is good for a guaranteed free point of karma.
Also see the introduction thread.