Twitter has many uses including competitive intelligence, but one area where it is limited is in providing metadata about its members (that is not a criticism - many members appreciate that). There is a whole industry devoted to analysing Tweeters based on what they say, but what about when you want quick search results based on their profiles?
It is possible, within narrow limits, to search for specific types of people on Twitter. The key is the "bio" field in Twitter profiles. So for example, this search reveals people on Twitter who are product managers. Granted, this is not very useful if you are targeting a specific competitor.
More indirect is a search for Tweeters who live in places that are the headquarters of a competitor. For example, this is a search for Tweeters who live in Cincinnati, the home of Procter & Gamble. Are they all Procter & Gamble employees? Of course not, but the results may be more useful than no results at all.