We've had a reasonable amount of interest in using OpenID to log into FogBugz. Expanding our authentication options didn't have as much bang-for-the-buck as some of the features that made it into FogBugz 7. Really, there was so much our customers wanted that just couldn't be worked around (still is), so we couldn't spend time on things that didn't provide tangible, immediate value to the end user. As FogBugz matures as a product, it's likely that we'll broaden the ways in which we can interact with the outside world. For now, the strategy is to earn business by delivering features.
Please vote up the question above to show your support for seeing this feature implemented.