Here's a case where Yahoo is trying to play catchup with other social networking sites.
I wonder if just a better mousetrap (in this case a better combination of features) is adequate for folks to switch over to a new site. Granted the individual switching cost itself is very less (meaning a user can easily create a profile to get started), there is a group/network switching cost which almost seems unsurmountable (meaning every other person in my network would also need to switch over to the new service). Leads me to think about whether first mover advantage is more important on the social network landscape than other sectors.
My take is that the very next generation of social networking features will involve a standardization feature (through some kind of standardized XML interface) which allows for people on different social networks to collaborate with one another — Similar to generic IM client (Pidgin, Gaim etc.) which allow users to connect log on to their profiles on AOL, Yahoo, MSN to see friends across all those networks (service providers) through one tool.