Dream by ~toshko on deviantART
Say Youtube, Deviantart or whatever. Once the publication starts to get 20, 30, 40 ... comments, communication is getting more and more pointless.
The author will read any of the comments? Come on. The visitors will read it? Give me a break.
In the best case, they will glance the first page they see, unless they have a special interest.
- Who cares do they read them? You write a comment, because you have a position you want to ... ooops.. share...
To yourself only? Why would you publish it then - you know your comment just by thinking of it, you don't need to type it if it's just for you.
Comments are intended to communicate, but actually the more comments written, the more you would be wasting your time, commenting, too.
Status and Fame
If you're not famous, you would greet every single comment or favourite you get, because it's "precious" for you, your peers show respect to your works.
While, say if you're a famous artist in Deviantart, you don't care that you've got 50 or 55 or 100 comments or faves per deviation, your respect to the others diminishes, they turn to your "fans", you turn to a "superior one"... Besides, you cannot physically "respect" them all, as they're getting more and more.
Cyclic "Self-feeding" Popularity
This happens on sites which promote the most popular items .
They are always shown and people click on them - that's easier for the user.
So they get more and more visits.
Actually, long lists of comments is useful for natural language processing purposes and automatic analysis of text. :)