simple script for blocking adds. add it to cron to keep your hosts file up to date. seems to work very well

jfBlockAds.sh

#!/bin/bash

#
# 05.31.12 JamesPFinn aT gmail DoT cOm 
#
# Script meant to be run from cron will update hosts file
# with contents from http://someonewhocares.org/hosts/hosts
# the contents will serve to block ads and other undesirables.
#
# Do not make customizations to the host file between:
#    #JFADBLOCKSTART
#         AND
#    #JFADBLOCKSTOP
# They will be removed on the next run of this script.

#
# Backup hosts file
#

sudo cp /etc/hosts{,.bak}

#
# Check if we have already updated the hosts file before
#

( grep "^#JFADBLOCKSTART" /etc/hosts |:) && PREMOD="TRUE" || PREMOD="FALSE"

if [ $PREMOD ==  "TRUE" ] ; then 

head -$((`grep -n "^#JFADBLOCKSTART" /etc/hosts | cut -d\: -f1`-1)) /etc/hosts > /tmp/hosts.tmp
tail -$((`wc -l /etc/hosts| cut -d" " -f1` - `grep -n "^#JFADBLOCKSTOP" /etc/hosts | cut -d\: -f1`)) /etc/hosts >> /tmp/hosts.tmp

else
cp /etc/hosts /tmp/hosts.tmp
fi

#
# Block the ads!
#
echo "#JFADBLOCKSTART" >> /tmp/hosts.tmp
curl -s http://someonewhocares.org/hosts/hosts | egrep -v '^#|localhost|broadcasthost|^$' >> /tmp/hosts.tmp
echo "#JFADBLOCKSTOP" >> /tmp/hosts.tmp

sudo cp /tmp/hosts.tmp /etc/hosts