My explanation for that difference used to be that BTC-e has relatively high fees, so arbitrage kicks in only when the difference is larger than the fee. The explanation why the difference existed in the first place was that more bitcoins were sold and more dollars flowed out of BTC-e than the other way around, therefore the bitcoin price was low, i.e. the price of the other major exchanges minus the fee minus some epsilon, so the arbitrage bots can make a small profit.
However, for a couple of weeks that behavior has changed to the exact opposite. BTC-e bitcoins are now a couple of $$ above the other exchanges.
One possible explanation is that recent irregularities, like the problems with US$ withdrawals, forced or scared people to buy bitcoins in order to transfer their savings out of BTC-e to safer places or at least to places with functioning fiat withdrawals.
Because I am easily scared (memories of Mt.Gox), I have now done exactly that too, and while I was working on it, the BTC-e web site disappeared entirely. That scared me even more, and I seriously thought I had lost my remaining balance, so when the web site came back, I emptied my account completely and withdrew all bitcoins.
What do you think? Is it true that people are buying bitcoins to transfer them out, thus driving the price to its upper limit? Are they justified in doing that or are they just cowards? What do you know about BTC-e?
The thing is you dont know whats going on @ BTC-e but from my experience they always processed my withdraws of which i made many when i was arbing. They could be holding the price up for some kind of arb reason or to attract more deposits. The price could drop below the other market leaders any moments and again be below finex for months. Pretty crazy, makes you want to deposit and sell.