I know this is an old post so I hope the mods don't flag me, but I must reply here. While I agree with new crabs you should give them time to settle in before handling them, it is not a crime to handle them over all. The title of this post makes it sound like you should never handle them. I know some members on this site keep them in the background and never interact with them, but I find that sad. Crabs are curious and yes, you should interact with them at some point. You need to learn how to handle them so you don't get pinched and eventually they will get acclimated to you. My current crabs Zoe and Gregory must not understand the rules of being a hermit crab because from Day 1 they have crawled all over me with no fear whatsoever. I have had experience with crabs that didn't like to be handled too and I gave them space. However, I find a crab that is incredibly fearful and not inquisitive almost always dies of stress. This is why when you go to adopt on you should let it crawl on you and see how it acts. Then you can build trust from there. My first crabs Magpie and Tappy got very used to me and my mom because I used to let them out to crawl around my bedroom floor to explore (they didn't live on the floor, I just let them out to explore). They loved it and it got to the point where if any of us walked in the room they wouldn't care. It took about a year to get them to this point. I handled them and let them take their time exploring me and getting used to me. I have friends who's kids built a Lego castle for the crabs to crawl in and they had such fun. Of course the crabs had days where they didn't want to be bothered and then I would leave them alone, but it's no different then when my dog wasn't in the mood.
So please, anyone who is out there reading this, please understand you can handle your crabs with care. Please educate yourselves on how to handle ANY animal properly. With crabs you'll want a flat, outstretched open palm so you don't get pinched. Eventually you can get your crab to trust you, and maybe one day get them trained well enough that they are calm when you take photos. When I select a crab, I look for one that is calm. I never photograph a crab who is in no mood. But after many years of doing this, I can say without a doubt that handling them can lead to a better understanding of your crab. Just ignoring a pet of any kind means you shouldn't have a pet.
Here is what handling can get you, a crab who sits still for 200+ photos without so much as a care. Meet Gregory (this is his old shell, he is now in a turbo):
Tappy, my former shutter bug, I could do anything with him. I could sit with him in my hand for an hour and he wouldn't move. When Magpie died, he sat with me in my hand and watched TV:
Big Oliver, 14 years old when he died:
Yes he was seriously the size of a softball. If you think he was in danger here, he wasn't, he was hanging over my pillow.