The twitter_blackbird module allows you to create an HTML representation of actual tweets in your posts, just by pasting in a tweet URL.
Twitter API:
http://media.twitter.com/blackbird-pie/
Demo:
http://www.universalpantograph.com/content/test-blackbird-pie-tweet-embe...
In addition, each HTML representation includes web intent links:
http://dev.twitter.com/pages/intents
that allow you to reply, retweet, or favorite the tweet.
Although every tweet is archived after first use, I haven't considered any more sophisticated forms of handling rate limits yet, because in my own use cases I'm not likely to encounter those limits. Soon. (I have not joined forces with the twitter module because this module has no dependencies on it. When I address rate limiting with OAuth, or for other functionality, that will happen.)
NOTE Because Drupal stores only data that is entered in posts, only the URL (and not the full tweet HTML representation) is stored in content. This may change in a future release. However, the twitter ID and twitter details are stored, so that the site only hits twitter once per posted tweeet.