1. How can I select the address I want to use for sending coins? In the sending dialog, I can only enter the recipient and amount. Is the sender address randomly picked from my address list? If, then that means the recipient can look up my past transactions for that address in the blockexplorer. So the more often I send, the easier it gets for others to build a map of all my addresses?
2. From what I read, if I received a lot of small transactions and make a big transaction, then those small amounts are bundled. Does that mean that my outgoing transaction contains a whole bunch of my addresses which also can be looked up in the blockexplorer?
3. Is the transaction fee voluntary? When I look into the options of my client then there's a 0.00 fee; but I read that 0.0005 is the minimum fee. I mean, why should I pay such a high fee like in the wiki? (See
https://en.bitcoin.it/wiki/File:Lfm_fee.png). To send 8.60, I need to pay 1.07?
4. In an older client, one could also send to an IP address. Does that mean that coins are transferred without appearing in the blockchain? Because if 1. and 2. are correct, I'll make a second "spending" wallet in my LAN and send coins to its IP from my "receiving" wallet. That way all my small transactions get converted into a single transaction which never appears in the blockexplorer.
(if this should go to another section, feel free to move it)