Lightroom 3.5 RC bug:
I selected a set of photo's across different folders based on a keyword. And used Web to generate a web site. But... two photos in different folders had identical names. The 2nd photo overwrites the first on the web site, and the 2nd photo gets displayed twice.
One of the many reasons I suggest eliminating duplicate filenames from the Lr catalog. I don't know if this can be considered a bug or not, but I do know if every file has a unique name this will never happen.
@Rob. Indeed this can be avoided by giving your photos unique names. This happened in photos that I received from multiple club members for processing. I preferred to preserve the original names.
I consider it a bug because Lightroom supports non-unique file names (across folders) but doesn't warn when there is a name collision on save-to-Web.
For Export, by comparison, the default behavior is to "ask the user" and offer the choice between overwriting the file and assigning unique names.
A satisfactory solution: automatically fix file name collisions between files written in the same save-to-Web. Overwrite without warning if the target directory contains files from any previous activity.