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Google's Picasa got an interesting new feature today: embeddable Flash slideshows to post your photos on blogs, social networks and the like. As you can see from the sample embedded below, they're vanilla flavor, with no fancy transitions and just simple back and forward buttons. So this is really more of a challenger to Flickr slideshows than any of the popular ones being used on social networks (RockYou, Slide.com, Photobucket).
And the other problem with Picasa is that it's so reliant on the desktop app: yes, you can upload photos and search public image using Picasa Web Albums, but it's hardly up to par with Flickr. Existing Picasa users should be pleased - for everyone else, it's not a good reason to switch.