Hiding aff links is really important for affiliates!
Not because of hiding aff links from users or something else because of not giving the casinos link power for free.
Few programs redirect the affiliate traffic from http://www.casino.com/aff=12345 to http://www.casino.com
A while i thought “how nice is that, looks much better for users”
But the casinos uses a 301 redirect code and google will transform the linkpower from http://www.casino.com/aff=12345 to http://www.casino.com and the casino get some really nice backlinks for free.