im pretty sure many of us aint usin the detectives that much. just to make them more useful :

idea 1 = They may be paid , for ex. , 50.000$ for each 10mins to find where a target mob is ..After 10 mins , we get a personal from them if they could find the target or not..this way , more you pay , more they have time to look for target and more chance of their may find the target easily..

idea 2 = Again , we set a target mob..but this time , detectives just follows the target and inform us on our personal whenever our target posts a reply or make a thread on any forum..this way , we may watch a desired mob's forum activities..

Btw, if you think that anyway detectives are bein used effectively and they are handy as what they are currently , then you may ignore these thread :-)