No seriously though, wasn't that half the point before it turned into the "omg we're a social network build your popularity and acquire all the followers to broadcast your brand" game?
Anyway, some UI fixes I'd suggest:
1. On open, prompt the user for what they are doing tonight with some auto suggestions (and the option to write their own).
2. Allow users to upload pictures for what they're doing (people love pictures)... aka social networks don't succeed without pics. At least let me take a picture of the event I'm at or food I'm making.
3. "Tag" users does not prompt any users for me (you should pull up my friends list or address book if I haven't added anyone).
4. Similarly, if I don't have Facebook friends on here, ask me to invite some.
5. Too much unobvious iconography in the app. Tags don't usually imply to people to me but rather keywords. Your edit button is a circle which is confusing. Also, be consistent and use "Go" when I'm inputing stuff.
6. Black, White and Blue are really boring colors. Add some flavor to this and make a custom footer UI bar.
Most importantly, I agree with dmix in that I need a reason to "cheerlead a new social network". You should provide some kind of incentive to solve the chicken/egg problem.
Here's what might work though: aggregate and map local, context-aware events: local as in things that are happening nearby, and context-aware as in things that suit my interests. Why not consume data from Songkick for example - like displaying concerts and music events. Or figure out a way to generate data from bars and nightclubs. Maybe mashup something from Yelp? Make it easy, fun, and intuitive to browse this type of information - with data from your friends mixed and layered in.
That way, there's a reason to use this thing without the luxury of having friends who are users (which, frankly, will be everyone).
I've been thinking a lot about this stuff myself - I'd be happy to toss back ideas outside of HN. My address is in my profile.
Edit: you may want to also take a look at our "nearby" events. While the list may admittedly be a little dry if you're outside of a high-populous area, it's a cool feature.
Rather than hunting for plans posted on Twitter and/or Facebook, you can always rely on doingtonight to find out what people are doing tonight, without having to sort through all kinds of unrelated conversations.
We also think people have a different identity at night, and don't want to mix that up with their identity on the rest of the social graph.
But you're absolutely right that we have to do a lot of work before we realize this potential!
Same with Path, I'd like to use it but I couldn't be bothered to cheerlead a new social network to them.
The same applies here, sadly.
