I'm the developer of a WordPress plugin that uses Smush.it ( http://wordpress.org/extend/plugins/wp-smushit/  ).  It dates from when Smush.it had a public API (when Stoyan and Nicole hosted it themselves).

Since Smush.it came over to Yahoo! and YSlow there hasn't been any official API support.  ( You can read more about this on my blog if you're so inclined: http://dunae.ca/2009/thoughts-on-smush-it/  ).

My question: are there plans, and is there a timeline, for a public API to Smush.it? I'd like to know whether I should decommission my plugin.