Delete thumbnails and the photos vanish too...

Last Sociable Hacker relates a story about his father's use of Picasa.

His father has Picasa installed, and one day found that all the photos had disappeared from the My Pictures folder in Windows. This was strange, since he didn't think he had done anything to cause that, though he did say that "I recently deleted some photos within Picasa but I don't think it had anything to do with it."

It turns out that he thought of Picasa and the underlying disk folders as being quite separate, and saw no reason why deleting items in one should affect the other.  This had been "proved" by deleting some items in the My Pictures folder before, when they remained visible in Picasa (well at least momentarily before the thumbnails were updated).

It's a tricky issue for Picasa to educate their users on.  One of the great points of Picasa is that it does provide isolation between the Picasa view of a photo and what is stored on disk - the Picasa view may include rotation, cropping, and image enhancements which are not visible if you view the image in another program, since (unless you explicitly use the "save changes to disk" feature in Picasa 2.5) Picasa does not affect the original on disk image.  However, this isolation does not extend to deleting images not affecting them!  To be fair to Picasa, it does put up a confirmation box when you try and delete images within it - but if your mindset is that you are only deleting Picasa's (thumbnail) copy of an image, then that confirmation box is unlikely to stop you from going ahead with the delete.