CyanogenMod has Profiles, but they are not profiles like you are asking. They have more of profiles for the type of notifications and sounds that can happen when that profile is enabled.
Supporting multiple users has been discussed before, and I think that it is something that is needed as well. If I buy a tablet, and set it up for my email, calendar, etc. I don't want that device to be a community device. Which would mean that multiple tablets would be needed in a family household.
A problem with being able to support multiple users is the space required. If each user had their own settings, then the /data/data would have to be much larger to support these extra users. But not only settings, it would have to support all the apps installed by the user too, so /data would have to be much larger too. You couldn't use the same apps between users, because the paid apps are tied to the account that bought them.
I think this will eventually happen, but much larger storage would be needed for the devices. As it is, my device consistently fills the /data/cache and I have to clear that out because of the number of apps I have installed. Now just imagine have 2 (or more users) using the same device. And where do you set the limit on the number of users that can use one device? There are 2 adults and 3 teenagers in my household. So that is 5 people that could potentially be using one device.
I actually experience issues with Google TV about this very topic as well. It doesn't, currently, have gmail, or apps like that, installed, but I can log in to gmail via Chrome Browser, and then if someone else comes and uses the TV/Browser, now I am logged in. (I don't actually do this, but I noticed it to be an issue with services like youtube and such)