There is a SharePoint 2007 form library whereby the filename is based on the following format - YYYYMMDD-HHMMSS and "duplicate files will be overwrite" option is enabled.
What will happen to both form submitted by 2 different person at the same time - meaning that both person submit, say exactly at 21 September 2011 06:06:11, thus giving two file of name 20110921-060611?
Last request wins. There is always some difference even if just few milliseconds.
There is however slight possibility that last request will receive some error if two saves are really, really close but in 'real life' scenario 1 second difference in names is more then enough.
If you want to be 100% sure use extra data in filename eg. name of the user who i submitting form. You haev userName() function in IP that you can use for this purpose (be aware of unsupported characters in user names eg. \ )
