I got bit this summer while getting out of the truck to go cut. I felt a sting like a wasp sting, and quickly brushed my leg. I did not see what kind of spider it was, but it took forever to heal. The center of the bite turned black and necrotic, and there was no feeling if you poked something into the hole. The surrounding area was red and swollen. I asked an instructor at school (nursing) and she said most complications either come from direct anaphylaxis to the venom, or from the secondary infection. Think about it, the skin is dead and there is nothing to prevent beta hemolytic (hemolytic means the germs can feed off of destroyed red blood cells) bacteria from infecting the area.
A septic infection can kill you, even if you are perfectly healthy and normally fight off sickness well.
I am healed up, but there is a knot of scar tissue on my leg.
The worst thing for attracting spiders that I have seen is cedar shakes or shingles, there is a whole ecosystem in there with spiders as the top predator. I like the craftsmanship of installing a cedar roof, but the spiders and bugs are not worth it.
Dan