I worked at eHarmony in 2009 and we had a monitor in the office which showed user complaints. Apparently, the business people had A/B tested and determined that the additional revenue from ads outweighed the annoyance that users experienced (I actually asked directly about this). The other thing was the large number of people who were frustrated by the low density of users in their geographical region. Spending a lot of time with user data as a developer was kind of depressing as a significant part of their user base was divorced people who were recovering from alcoholism or drug addiction.