The transaction ran Out of Gas, as can be seen on https://live.ether.camp/transaction/abddd676a2dc65dc4790463121bd77cafce4e0fb878d0b386556b055e0cae2d0/vmtrace#0
Here's the transaction where the 100 Finney was sent and it shows "Gas Limit" is 21000:
So the user (0xbf27f..) specified that the transaction can consume up to 21000.
21000 gas is exactly what's required in Frontier, for a value transfer.
You can see from here (deselect other filters except for "value transfer") that 21000 gas is enough to send any amounts of Ether.
So why did the transaction run Out of Gas?
Because the transaction was a contract invocation (see upper right of image)
Let's take a look at the receive address:0xe358b3b9f29c67cb810c5184e6fde27d66ce036c
See how it has code? Whenever a transaction is sent to an address with code, that code is invoked, starts getting executed and consuming the gas, just like a car consumes its fuel. If the gas is depleted before the transaction is able to complete, an Out of Gas exception is generated and basically everything the transaction did is undone. That's why the 100 Finney remains with the sender.
From the transaction if you click on "vmtrace", you will see the Out of Gas. This transaction didn't have enough gas to even do a single computation step, but if a little more gas provided, the vmtrace would should some computations being performed, until the point of Out of Gas.
Specifying more gas would prevent the issue. It is safe to specify more gas, because any unused gas remains with the sender.
For example, if 123456 gas was specified and the transaction only consumed 50000 gas, the remaining gas (73456) would remain with the sender.