Mom's Club...who do you let join the circle??

So, I was speaking with a friend about our "circle" of moms. I have been very fortunate to have made a handful of very good friends these last 4 years. These truly are friends I think I will have forever....and I met them because of my children. I used to work in the corporate world in NYC and when I became a SAHM, I joined everything I could find.  I went to the library, I took classes, I talked to any mother I saw at the grocery store just to make some friends who where in the same place as I was. And thankfully it worked well. Don't get me wrong, there have been some psychos along the way...but all in all, I have had good experiences. So, needless to say...I met a SAHM through a friend that seems like a nice person. But you know when you know that you are just not joining to click with this person. It is like going on a date....the chemistry has to be there. You check out your date...how is he dressed, what kind of car does he drive, will you have fun with him??? Well....let's admit, we do this to other SAHM's. Will she fit in with my other friends, will our kids get along when we go the park? I know this SAHM that I met will not fit in my "circle" of mom friends. Where do you draw the line.....as a SAHM, are we supposed to let anyone in our club?? I am going with "no"......I have enough friends : )