Yes there is a very nicely detailed explanation of shifts earlier in this thread. To simplify it for you a shift is a less granular look at your contributed hash rate than tracking every submitted share. Makes it easier on the pool to track shifts instead of shares.
Renting for profit is tough to pull off. Phil got lucky. He got hashing power at a very nice rate and the pool found more blocks than expected. You can also get burned playing this game. For example, a few months ago I rented a large amount of hash. Unfortunately the pool on which I was mining suffered some horrific luck and I lost a lot of coin.
the above is true.
lets say going rate is 0.0105 a th and you get 0.0102 a th you rent 100th which is 1.02btc which is .03 under the going rate. to do this alone is very hard and it just means you rented at a discount.
You pick a pool and hash and the pool sucks make hardly any blocks = you get fucked and lose. even though you paid a good rate.
In this case I paid a very good rate and the pool whaled = the best of both worlds.
Kano's pool is the best ppns pool to do this because the 500% gives more days of hashing having earnings which tend to flatten the risk out a bit.
here is what is left of my earning power. I ended on a high rental this keeps the avg up I was
100-100-100-100-10-10-10-10-10-10-10-10-10-80 more 10's-200 I am left with some of the 10 rentals and the 200 at the end my avg is down to 4.84th
4.84/1800 = 0.00268889
0.00268889 x 25 = 0.067 btc if we hit a block and that will decline.
the key to renting get a good price. High---low---high.
I did 100 then 10 then 200