Hey Ray, I commented this on another thread but will copy the message below too for reference:
The reason we built in the click to play feature is to keep a page with several embedded synths from bogging down. It's pretty common for this sort of thing to be set by default.
You can make an easy change to the embed code to set the synth to autoplay. In the code you grab to post on your blog look for the "&delayLoad=true&slideShowPlaying=false" part. If you want the synth to autoplay, swap true for false and vice versa... ie, "&delayLoad=false&slideShowPlaying=true"
P.S. It isn't just accommodating Mac people... we're accommodating everyone who might want to see your synth but hasn't downloaded and install the full Photosynth program. With the Silverlight embed you'll be able to share your synth with a lot more people PC & Mac.