Well, I don't know if I really have ten reasons, but Craig Roth has some interesting thoughts in Why Do We Care About Top 10 Lists?.
... I see the “top 10 list” phenomenon as a good analogy to what a slew of technologies at the intersection of portals, RSS, and social software are trying to do: filter out all the noise and just bring me the important information, encapsulated, all in one handy spot. It is a commonly recognizable form of attention management.
I particularly like his setup of the idea of a "permanent Top 10 filter" that would bring me articles / movies / music that only fit my Top 10 criteria.
For bloggers and people heavily vested in social media, this idea of attention management isn't terribly new. However, Craig adds more detail around how this social filter idea works. Specifically, he highlights five elements:
Integration: Connecting up with all the event streams, information sources, and data
Categorization: Determining what subject the event falls into
Rating: Prioritizing this bit of news. This is probably the toughest part of the process at the moment, but attempts have been made in the form of social ratings engines (Digg) and attention profiling (APML).
Personalization: Lining up the category against the set of subjects that you are personally interested in, either through explicit declaration or implicitly.
Display: A UI that presents the user with capsules on each of the items and allows the user to notice, track, and manage the information.