Since version 1.6 or so, simple-adblock implemented Dirk's (author of adblock) ingenious system of shrinking the dnsmasq file by removing extra entries. For example, if after downloading block lists the block file contains entries like:
advertising.com
www.advertising.com
www1.advertising.com
ads.advertising.com
the last 3 entries can be removed as long as advertising.com stays in the blacklist.
This takes a few extra seconds to process/start but it leads to reduced RAM usage.