Having really great domains might do the trick for concentrating on just 1-2 domains. If you own pizza.com/newyork.com for example, you should probably put 95 % of your effort in developing that domain and just park the rest off your mediocre names.
I fear many of us do not have those killer names which are worth so much that you are better off neglecting the rest.
I choose to develop many sites in order to be able to show as many domains/get some visitors to the sites as I can in order to sell them.
Being an expert about 1 particular subject might be a good reason to make 1 great site about it as well,as you could relly add a lot of value to a domain with that subject,but I do have no such subject.
Having 1 or 2 really outstanding domains like geo's might make people concentrate on those and invest say 60 % of their time in them and 40 % in developing other domains.
Elliot's blog has been about this subject once.
His ideal was to have like 5 great geo's or so in 10 years time and a few more sites for friends/hobbies next to it,but to stay away from all the mediocre domains/sites.
I basicly have only bad and mediocre domains, so therefore I may be better off developing many a little bit(or throw them away).
Another reason for building many ok sites is that it is a lot easier to make many ok sites than too build/find someone to build great sites.You spread your risk as I saw someone say on a similar subject.
In order to build great sites you better have really good ideas and the skills to execute/have money and/or know people who can do it for you.This therefor contains a lot bigger risk.
I do not know whether great looking sites make exponentially more money than many mini-sites,if someone can prove that things might change.
Same is valid for what kind of mini-sites make more money,can change from subject to subject.
Just like with parking and developing mini-sites,there seem to be very few valid rules for what works best for which kind of domains.Little"scientific" reasons done/published.
Another reason for developing mini-sites is to lay the the base for a more expanded site and work your way up in the search engines already.
I fear though that expanding the sites,adding more things too them once you get more time/money will just stay an idea,but not really happen as buying more names and adding mini-sites seems easier.
