No they are not. They are part of the same phylum (Arthropoda), but so is everything else with an exoskeleton and jointed legs. In fact the "family" classification of species comes below both crab and spider (there are different families of spider, but crab isn't one of them)

Being in the same phylum is not particularly special for most species, particularly if that phylum is arthropoda, which has well over 1 million species. For comparison Humans are in the phylum: chordata, which is mostly ascociated with the sub-phylum: vertebrate... which includes all mammals, birds, reptiles, amphibians and most things people class as fish.

(n.b. I wasn't meaning to be condescending by the way, I just knew they were not the same family and have learnt/re-learnt a few things myself in finding out where crab and spider are in the order of species)

You made me sad face.

Sorries. Here have a spider hug and a crab hug.

In seraching for a crab hug I came across this beast:

Apparently it's called a coconut crab and is the largest current species of arthropod that lives on land... not sure I would want a hug from it though.

These buggers made move out, no kidding. I made a thread whining and being sad about it too

Ewwww...  I don't like bed bugs.  I've seen programs on them a few times.  The kiss of death bed bug ( http://www.sciencedaily.com/releases/2010/04/100429111012.htm ) is really scary since if it poops into a cut or bite then you will get really sick and possibly die.  I also seen the programs of the microscopic bed bugs that just live in your mattress and you can't really do anything about them.  I learned that due to the stopping the use of DDT (which is a good thing for most species (especially Bald Eagles)) and other strong pesticides that the bed bug problem has come back.  The fact that they can jump onto your luggage and fly with people doesn't help contain their spread either.  So a hotel in a major city (New York) could be fine and not have any problems until a traveller who shows up with them.

Those are the ones I am talking about. They are not really microscopic but yeah, I SPENT days looking and I couldn't spot them. I was almost convinced that something else was causing my skin rash until I woke up one night to study for an exam and found one sucking my foot lol. You are right about DDT, but  It's not just that anymore. I don't like bedbugs obviously, they are gross. I just thought they were worth mentioning. I think they are the strogenst bugs man will ever have to fight, they are here to stay. They can't kill you but they can drive you crazy. Also, wb :)

Bold part - You must have missed my link because there are some that can kill you (pass on deadly diseases).  They are mainly in South America and other places though.  Basically, bed bugs almost makes me not want to travel since they are prevalent in public places such as hotels (not having any money to travel helps not being able to travel).  It is quite scary just to read the articles but it is also pretty fascinating (especially the way they developed resistances to the chemicals that we try and eradicate them with).  I was thinking in the back of my mind about drug resistant bacteria and lo and behold the first article eventually brings up that comparison. 

The second link you provided was pretty nice too.  I found this part kind of funny...

"5.       When it comes to evaluation and treatment, visual inspection remains the most common method pest professionals use to determine if a bed bug infestation exists. However, the use of canines has grown from 16 percent to 43 percent in the past year."

I know dogs have excellent sense of smell but I never heard about them being used to detect bed bugs.  On a semi related note... There seems to be a huge flea outbreak in my area (Austin, TX) and a lot of dogs seem to be suffering from those pesky fleas.  Good thing they can only bite humans and not live on us!  They might be able to live on some hairy Neanderthal.