[atombender]

I don't know for sure, but I'm pretty sure they're combined behind the scenes. Fractional shares are really abstractions over an underlying instrument. The broker is the actual owner of the shares, and you have an indirect ownership. Among other things, it leads to a situation where you cannot take part of normal shareholder activites such as voting. The broker still needs to keeps records of the cost basis of each fraction you purchased, of course.

[ipqk]

This is generally true of whole shares too – that the brokerage technically owns the shares. And why brokerages will set up proxy voting for shareholder activities.

[perl4ever]

The broker is the "actual" owner of whole shares too, isn't it? You know, "in street name"?