Writing about other sites

I have seen many posts by members that write about other writing sites. Although referral links are banned other members can reach those sites and if they provide better facilities/money etc persona members could shift there.

I just wanted to know what benefit persona gets in letting members to write where even sometimes explicit mention is made of sites that are a better player. Would you, if you owned a writing site permit such posts? I would not specially if I had just about launched a site.

The magnanimity of persona cannot be under estimated but I think charity begins at home.

What say?