It would be nice to be able to mark some versions as 'unresolveable', by which mean that you can't resolve issues with this version as the 'fix for'. Versions are a helpful way to organize tasks, so it's not uncommon to create a fake version or two to hold groupings of tasks ("current release, unspecified iteration", "future release", "pick-up tasks", etc.). However, if these are resolved, we often want to know the 'real' version in which they were resolved, which is where using 'fake versions' bites you. This could be met by allowing another method of task categorization so that versions wouldn't be used at all; I'm not entirely averse to this approach.