We have spent a lot of time in Twitter the last few weeks… a lot.  A few quick observations of things we've noticed:

• Twitter is down all the time.  I'm not talking about the consumer front-end… I'm talking about the API.  Folks there who work on stability/network operations must be some of the most nervous and downtrodden people you'll ever meet.
• I'm sure the cause for this is the rampant proliferation of applications built atop Twitter.  It will be interesting to see if Twitter purchases some of these companies or if they make the API more robust to allow for bigger, better things.  My guess is that both will happen.
• Twitter API limitations are understandable, yet curious.  Biographical data each Twitter user requires a separate API call.  I presume this is both a technical limitation and a business advantage for Twitter — as long as they know who Twitter users are in real-time and you don't, they can develop more interesting applications.  I know a lot of developers who are circumventing this in one way or another.
• Twitter has far more junk/spam users than people think.  Based on random observation, my guess is that it is at least a 2:1 ratio, maybe more.  eMarketer assumes there are currently 18 million legitimate Twitter users.  That's probably just a little high assuming a 2:1 ratio and Twitter's recent estimate of ~45 million users, but my guess is that it's in the ballpark.

Finally, a quick note about Facebook Lite.  I have looked extensively at Facebook Lite and I'm not terribly bullish about it.  Facebook users are different than Twitter users IMO, and they don't need a streamlined interface.  Facebook built Lite as a reaction to Twitter, not as a reaction to customer feedback.  I think they really should stick to their strength and not worry about Twitter.  More on that topic later.