I don't think you really know either way.What you can do is create an honest dialogue with people that might help you to find your next role. Explain to them that you are taking your approach to finding your next role very seriously, but that you realise that the competition is intense. As such you do not want to give out names of companies that you have already applied to yourself, for obvious reasons. However you should make it totally clear to them that i) they let you know beforehand if they are going to send your details to a firm ii) in return you will always let them know at this point if you have already applied to them, to avoid duplication. Use your softer skills to make these points in conversation sound clear and honest, reword my points if necessary, but you will find it is generally effective.Also logically it seems impossible to tell the 'idea thiefs' from the 'honest professionals who want to avoid duplication', but in reality you can use your instincts. For example agents that have lots of typo's in their ads, have an unpleasant manner and come from an agency with a poor reputation, tend to fit into the first group. Agents that are approachable, have good people skills and come from agencies with good reputations tend to fit into the second category. Why should this be? Not really sure, but I suppose generally the good agencies do not have to resort to underhand tactics.