I was reviewing the internal spam checking and I noticed that it is checking for blacklisted words.

When I went to yaf database, I noticed a table called yaf_Spam_Words containing only 31 records i.e. 31 spam words. I would have expected this table to be filled with a lot more spam words.

Question: Why is the above table only filled with so few spam words? My understanding is that spam services like Akismet use a lot more spam words when checking for spam and that makes these services more thorough in their spam checking.

(NOTE:I am using yaf 2.2.3, so may be in newer version there are a lot more spam words.)

Question: Why is the above table only filled with so few spam words?

Because this are the words i tested here in the support forum, and i manually add them when i find patterns. But you really should consider using Spam checking during registration. Which catches 99% of all spammers via BotScout.com and StopForumSpam.com. This is definitive the better solution.