No, not the potential ones for when your book is published, but the ones who point out all the flaws in your work in progress?
I recently joined an online crit group and it's my first one ever. Now I wonder how I could have gotten this far without one. It's helping me become a better writer. Reading and line-editing others' work helps you notice things in your own. I also thought my book was almost ready to query agents. Er, not so fast Mr. Prince. Now I see how much work still needs to be done.
Fortunately, I'm lucky enough to be with some really good writers and I'm glad to be in their company. Before joining, I imagined I would send the book to a few readers--some relatives and friends that have young kids who read MG and YA. I think I'll still do that in the future, once the book is the best it can be.
So who are your trusted readers: spouse? friends? yourself?