Think about why you want the cash, and the answer should become clear.
I don't especially want cash at all, other than to have enough to cover day to day cashflow. But I do have a checking account, and it does have more than one month of expenses in it, and Mint and Vanguard both include that checking account as part of my total assets. So in addition to stocks and bonds, some small percent of my net worth is currently sitting in a checking account. Listed as cash in my asset allocation.
I don't even especially feel the need for an emergency fund anymore. We have enough invested (at our chosen stock/bond split) in our taxable account that we could live for good long while even in a market collapse. Years, probably, available on three day's notice by selling mutual fund shares.
But it feels silly to keep your checking account bouncing off of zero every month if you have millions of dollars in total assets. Surely there is value in keeping some cash buffer around, but I haven't yet decided if that buffer should be a fixed amount or if it should grow along with my net worth.
Example 1: struggling consumerist schmuck lives paycheck to paycheck. He needs to build a few months of emergency fund before he can start investing. His asset allocation is essentially 100% cash at first.
Example 2: Warren Buffet is worth 50 billion dollars but has low expenses. Do you think his checking account has more than $500 in it to cover his groceries and gas money?
Everyone else is on some continuum between those two, and I don't think it's a straight line.