0.71 coins per day

There are two words missing "on average". Some days you will make more some you will make less. The whole thing about mining is that it is not fully predictable. If you want predictable exact income everyday, join a pay per share (PPS) pool, your income will be slightly less, but it will be totally predictable. The pool owner takes the risks and they charge you for taking all the risk.

If you were solo mining the following statistics would apply at the current difficulty of 1,564,057

http://www.alloscomp.com/bitcoin/old_calculator.phpProbability Time

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Average 70 days, 16 hours, 22 minutes

50% 48 days, 23 hours, 50 minutes

95% 211 days, 17 hours, 54 minutes

Every 71 days on average you would make 50BTC+fee (assuming that difficulty did not increase)

[50/70.666666666 is 0.70754717 BTC or rounded to two decimal places 0.71 BTC per day on average]

After 49 days you would have a 50% chance of solving a block and earning 50BTC+fee (assuming that difficulty did not increase)

After 212 days you would have a 95% chance of solving a block and earning 50BTC+fee (assuming that difficulty did not increase)

If you honestly really are worried that some pool is cheating you then log the output of your clients to file, and compare accepted shares with what the website says that you have submitted. On most pools, your income in Bitcoins should be 50*(your_shares/total_shares) for each solved block. Almost all pools have this information on their Stats/Blocks/History pages.

EDIT: My 100th post