Yes, ads.
It's a difference of attitude.
I found a snapshot of their site, here are a few bits from their FAQ:
"
Also, please keep in mind that you're watching videos for free as opposed to spending over 20 dollars at the movie theater or purchasing a show. This should help you put things in perspective (keep in mind that prices change but this is a normal, typical price). " ... snipped price list ... "So, as you see, you're saving quite a lot of money (especially when putting several visits to the theater or seasons together) by having to wait a little bit of time. "
Their main listing page is broken up into genres, which shows they were aware of the nature of their content, and includes heading that indicate the source of the content: "Movies" "TV" "Anime", etc. They don't even make an effort to hide what they are doing. Their submission page mentions "Copying the name of the show exactly as it is on imdb".
As for the issue of linking, it's a red herring here. This was not some neutral site linking to random, user submitted comment. This was a curated collection. They knew _exactly_ what they were doing.