The means of production model depends on what the country you're applying it to is like. If it's dominated by agriculture, then those who own the agricultural land are the upper class (even if they farm it themselves?). In an industrial society, it will be the factory owners. What about somewhere like Britain, which is dominated by finance? Not that I would say most city bankers are the upper class - they may have lots of money, but their political influence isn't high enough. The ones who control the media? If you're in an information economy, it will be the ones who control the information...
...which means that everyone's upper class, or will be when Anonymous and Wikileaks formally fuse together, resulting in everyone having all the information they want. We're already at the point where everyone can control their own means of production of information, and have been since we made the first scratch on the wall of some cave.
A traditional Marxist interpretation is certainly laughable in a post industrial society full of independent farmers, where there is no definite class that owns the "means of production". The only realistic way we can divide the classes now, if we were inclined to do so, is what their job entails - do they work for themselves or an employer, is their work physical labour (i.e. builder) or intellectual (i.e. teacher) etc. Or do they have to work at all, in which case they're either upper class (have enough wealth they don't need to work), temporarily out of the class system (unemployed but looking for work), or underclass (unemployed with no intention of changing that, what the Daily Mail call benefit scroungers)...