Understanding transactions, tracing BTC

Hi all,

I've been trying to understand some transactions on the BTC blockchain and have some pretty basic questions, i think.

Why do so many transactions point to an address with a 0 balance, and a 'symmetric' flow? that is, there are two transactions, one input, one output, and they are equal. I thought addresses where 'temporary' addresses that pointed to a wallet or something. Why do I see a bunch of addresses that have just one in one out that are equal? (See the example below actually, it is a bunch of transactions in a row that are equal, leaving nothing in the addresses).

Also, I see a lot of transactions that are just long chains of small losses. I dont know how to describe it, but there is a transaction that is for 1 BTC into an address. Then we see a transaction out that is for .9 BTC to one address and .1 BTC to another. If I follow the .9 BTC address, I see it goes to an address with an output transaction of .8 BTC and .1 BTC, and so forth. What is going on here? For example. start here and you see the output to To two addresses, one for a large BTC amount and the other for relatively smaller. Click the Large address, and you see the same thing. Keep following the large amount address. It goes for a while. What is happening?

Final question, these transactions often start or end at an address that is linked to an exchange. Have I just traced a single user moving stuff off an exhange and around on their own adresses, or am I chasing BTC going from different people to different people?

Thanks for any insight!