what i think it boils down to is that many folks seem to run default-free because they can, because its cool, because its what tier-1 folks do, because (insert cool/uber reason why here), but not necessarily because they HAVE TO.
Consider a regional or local ISP providing BGP to a customer. The customer also has a connection to a "Tier 1". The customer may start asking questions when they notice they get 250k routes from one provider and only 50k to 80k less routes from you.
It is all in the education. Educated right, you could claim that you're providing a superior service by _filtering_ what announcements you accept. better yet, you can claim that you're saving the customer money - THEY don't have to invest in more RAM / larger routers / larger TCAMs. OR, money dynamics will be that you charge a higher price for customers that want a 'full feed' with the higher price based on the higher price you have to pay to run a default-free network. the reality is that for many end customers (even multi-homed ones), receiving a 'default' route from an upstream rather than a ton of more-specific routes is perfectly acceptable. they can filter out that 0/0 if they don't want it, otherwise "things still work" if they accept it. in short: it is a MYTH that folks THINK they NEED a full routing table. most folks don't. cheers, lincoln.