Your odds of finding a block are the same running independently or all off the same server. You are not working towards a goal your are making many many attempts that each has a very small chance of success.

1. the wallet.dat file is all that needs to be backed up. As you create new addresses you will want to replace your backup copies. The wallet file generates some addresses ahead of time (starting as soon as you generate your second address) but if you run through those and start using addresses not in the old file you could lose the bitcoins sent to those addresses.

2. If you move the wallet.dat file somewhere else bitcoin will create a new one when it does not find the old one.

3. It only creates a new wallet.dat if it can not find the old one.

A second worker is only likely to help if you see the GPU consistently running at less than 100% utilization or dipping in utilization when waiting for more work.

If someone found a way to easily crack the private keys any bitcoins they stole would become worthless as soon a people figured out what was happening.

However it would not necessarily be the end of bitcoin. As long as there was still a secure public/private key system to switch to bitcoin could use that. Then we revert to a point in the block chain believed to be before any thefts took place. That would be non trivial and very painful but it could be done.

If a second transaction (probably with a fee) using the same coins gets in the block chain first the first transaction is invalid. However there is no reliable way to get the current client to produce such a second transaction.

As long as you don't lose your wallet.dat file you will always have access to all your old addresses. The address book in the bitcoin software stores a list of all previous receiving addresses.

Is your electricity really 90 cents per kilowatt hour? Mine is only 10 cents per kilowatt hour.

It is normal

Using a new address every time makes you harder to track, and it makes it easier for you to track where the bitcoins came from.

You do not lose the old address unless you lose your wallet.dat file that stores the private key for that address. Click on the address book in the bitcoin software then click on the receiving tab to see all of you previous addresses.

Difficulty does have a small effect on price.  When difficulty is high relative to the price, people looking to invest in bitcoin are more likely to buy bitcoins than hardware.

Your point seems to be that bitcoin is not a good store of value, even if this is 100% true bitcoin can still succeed as a medium of exchange.

A pool operator would have to be able to pull off a very large double spend to offset the long term losses from people leaving the pool for good.

The number you see the bitcoin software is the amount of power your cpu is contributing. You do not need to have the generate setting turned on to use your GPU for mining.

When solo mining you will see nothing at all till one day you see 50 coins show up all at once (possibly a little more from transaction fees). If you want more consistent earnings join a mining pool.

Difficulty is what is adjusted to make sure the rate of block creation (and therefore bitcoin creation) stays at a relatively steady pace.

To fund all the visible bids in the order book there has to be over 45k USD.

If anything is pushing non professional miners out it is heat (and to a lesser extent noise), not profit. Most are using existing hardware, and some have their PC running 24/7 anyway thus the only cost is the difference in power usage between idle and full load.

No but only because humans are really bad at producing truly random numbers.

A share does not help does not help the pool unless it is also a valid block what it does do is prove you where trying to find the solution.

A round that has been running for a long time has no better odds of finding a block in the given time period than a new round would.

I have a fairly crappy net connection, so to deal with it I run one copy of poclbm with a -f of 30-60 connected to the pool and a second copy with a -f of 200+ solo mining. The second copy gets about 5% of the gpu power when both are running but it picks up the slack immediately if there is a delay in the get work.

Edit: I have a satellite internet connection plus I use a VPN to avoid the 250MB a day download cap, but that puts me last in line for getting any bandwidth. About the only way my connection could get worse is if i used Tor as well.

Assuming they both work fine, how much would you want for the spare?

It is the bitcoin client that is using your CPU. Turn off the generate coins setting. It isn't needed for mining with a separate mining program and there are better cpu mining programs.