The reason the default is currently 10 is just conservatism: it was already an order of magnitude better than what it replaced (a *single* representative value) and I didn't feel I had the evidence to justify higher values. It's become clear that the default ought to be higher, but I've still got no good fix on a more reasonable default. 100 might be too much, or then again maybe not.
My hands on experience is that 10 is plenty except for the minority of tables within a database. Those table can be accurately represented using alter table without having to adjust the global.
That being said, 10 is fairly small and I often find myself setting the value to at least 250 just to keep it out of my way.
Sincerely, Joshua D. Drake -- === The PostgreSQL Company: Command Prompt, Inc. === Sales/Support: +1.503.667.4564 || 24x7/Emergency: +1.800.492.2240 Providing the most comprehensive PostgreSQL solutions since 1997 http://www.commandprompt.com/