Secondly, as someone who spent 15 years working with Lotus Notes, I can assure you that you can run it standalone. Obviously it makes no real sense for a Groupware product, but it can be done. To the Notes client opening a database locally or on a mail server is largely the same.
The main issue is that people used Notes to communicate and collaborate. So you could just go creating new Address Books, Discussion databases, Document Libraries and so on, but what exactly are you proving with that? It's be like just firing up the Microsoft Mail client and only looking at the address book...
Whilst I'm aware that there's plenty in Notes that people didn't like, I do think that there are some gems hidden in there which it would have been nice to have kept. The Notes dialect of Rich Text had a couple of niceties (programmable buttons, collapsible/expandable Sections). The database engine itself was unparalleled at the time, and in some ways it still hasn't been bettered.
But the issue remains that you'd need to set up a Notes/Domino Server (depending on your version - 4.5 onwards it's called Domino), and a small network. And that's a ball-ache that nobody wants. It can speak IPX/SPX and NetBIOS, so it doesn't have to be as complicated as TCP/IP, but it's still a lot of prep work before you even get to start looking at the usage. :-(
That having been said, I was a Principal Certified Lotus Professional on the Sysadmin track for about three versions of Notes, from 4.6 to 6, and can definitely help if you ever did want to do that. Feel free to email me at phil [at] philipstorry.net if you're ever so lacking in subjects that you feel forced into this last resort.