I think of there being two major ways to manage one's money: keep it all in one place or spread it out among many institutions.
The trend of banks and brokerages offering bonuses for new accounts can lead to a dispersal in ones funds. I personally am always tempted by the various offers (My Money Blog has a lot of the good ones...), and often succomb. The problem then is, you have another account to keep track of. Another user name and password, more statements, more potential tax consequences.
The simple me wars with the frugal me on this issue. The simple me wants just one institution, maybe two (a bank and a brokerage). The frugal me wants to get as many extras as possible, whether it be free trades, account bonuses or iPods. Who will win? So far, it's frugal me, but when it's time to do this year's taxes, well, simple me may need to take over!