I think you should feel free to bring it up whenever and however you want to, but I admit that I don't have a lot of hesitation about researching therapists. It seems like he should realize anything he puts online -- particularly in his professional role -- is fair game for his clients to know about and to want to discuss. I have found and skimmed some of my T's published articles and her dissertation, looked at her website, etc. But I also don't feel particularly guilty about looking at her Facebook profile either. My T knows about all this stuff and has asked about what it means to me and/or why I do it, but she doesn't seem upset about it and has never indicated that she wants me to stop.