At 100 sites and growing, Stack Exchange is becoming a host to many different communities with varying interests (and sizes). Is the aim of launching new sites, to make them (eventually) big communities like SO? Or are smaller and niche communities also considered desirable?
Also, what type of communities does SE consider desirable? Say, an open community with users of widely varying skill levels such as SO or a closed (unwelcoming to newbies) community of professionals* ?
*I am not implying that communities of professionals are unwelcoming to new users. In some cases, the standards set by such groups may be too strict for an amateur or a hobbyist (or may at least be perceived as such, which in effect does make it unwelcoming to a portion of new users).