About dating, I really thin that facebook, plentyoffishes and so on, have hurt nicely the $$ dating sites, as it is so easy to find local people in fb to deal stuff (esp. affairs). But I don't run dating program so I can't say. About cams I know more. It is not "hurting" the cams sales total (for big cam sites who adapted), it is however "changing" the cams sales process, and hurting the single cam model (per cam model) sales.
Tipping 1 token (few cents) per week, thinking it is a big gift, it is popular
Let's say the top 5 cam sites was making $X in 2005, these top 5 are probably doing the same $X in 2013, just are not the same sites, for example MFC replaced someone else who did not adapted. Also, the total models online to make $X it was less in 2005, but simply the sites got 5-10 times more models online, so the same $$ is made finally. Hosting is cheaper now than in 2005 so it balances the more leech.
Starting cam sites always been a problem, today is a problem for a little different reasons but I think the ease of failure for new cam sites it is stable in past years, simply most failed before and most fail now.