So, I think bitcoin sort of shot itself in the foot with the low number of total bitcoins. I think if the actual $ value per bitcoin was more in line with the dollar, people would be more willing to spend them. Yes, you can spend fractions of bitcoins, but for instance here namecheap wants at least .1 bitcoins deposited. Currently, that's what, $80? why do I want to give them $80 when all I really want is 1 $10 domain? How about a 100/1 split :-)
I think a split would motivate speculators currently mentally deterred from the idea that this virtual thing is "so expensive". They'd rather own 60 coins than 0.6 of a coin.
Here's this virtual coin that a low level speculator can't even buy a full instance of. That has to put off a few people.
To achieve similar effect, some people are proposing changing the default unit to mBTC, uBTC, or satoshi. While it is not splitting, it should have similar effect. Instead of saying they own 0.6 BTC, they'll say they own 600 mBTC.
That's entirely a psychological issues. There have been efforts to try to get people to switch to mBTC or whatever, but I don't think it will happen until the price is significantly over $1000 (and thus $1 == 1 mBTC)
