Here's one abstraction of swoopo that might be fun to
think about.  You might call this "Throwing good money 
after bad".

Forget about the payment for the item itself. Winner takes it 
with no payment. 

The house provides a hat and the bidders can throw Sacagawea 
dollars into it. The clock counts down from 10 seconds, and 
if a dollar is tossed in, the clock is reset. When the clock 
reaches 0 for the first time, the most recent contributor, 
say bidder i, gets the item and it's worth v_i to her. 

Let's say the number of bidders n is known to all, and the value 
distribution is known. 

Waiting till the clock reaches v_i minus an amount you commit 
to bid beforehand can't be an equilibrium, because no one would 
be the first to bid! (Although that might be a reasonable analogy 
to sniping in a real situation.) I'm thinking an equilibrium 
might be a mixed strategy where bidder i tosses in a dollar 
with prob. w(v_i), where i haven't the slightest idea what w(v) 
might be, except that it should be increasing. (By an argument 
like preference revelation that shows an equil. strategy must 
be increasing.) 

How would you play this game?! 

      - ken