Some of them mention it in their terms. Here's a little snippet from Adultswithbenefits.
"User Experience. AWB employs mechanisms and technologies designed to enhance the overall experience of the website and encourage member interaction.." "...This includes the design of Digital Lovers (DL). AWB creates an enhanced experience for our subscribers, members, and/or users through our "DL" services. Acceptance of these terms, all subscribers, members, and/or users understand fully, agree to, and accept this service. These subscribers, members, and/or users agree that select profiles and Members brandished to them may be constructed to promote subscriber, member, and/or user participation and activity in all of the Services. The DL services include posting pictures, information, conversations with the subscriber, member, and/or user's profile. The enactment of our DL services is to encourage and create account development, increase the subscribers, members, and/or users experience, quality control and to ensure acquiescence to these Terms."
