Robert Scoble hits a point (two actually) that I’d been meaning to write-up as well about anti-features and privacy wich are very very important for mainstream adoption of your webservice.
There is a movement in design which says that design and the affordances it creates has values embedded in it. Not considering the potential for abuse your design allows, can be deemed bad (because negligent) design work in itself.
Among the techminded early adopters I know, use of such applications already isn’t as clearcut as some of us would like to think. A lot of people aren’t comfortable broadcasting their location to the world at large (or to a massive American company). Just talk to a ‘normal’ person about this and see if they don’t get absolutely freaked out.
There are two aspects which are both very important though they may not seem so at first.
The Presentation of Self in Everyday Life
Firstly “presenting [yourself to] people as you’d like others to see you” is very important as discussed in Goffman and countless studies on social posturing and signaling that have followed. This is an important human need and basic freedom.
Privacy of Location
But more pregnantly for the mainstreaming of your application Scoble says: “(and if I’m freaked out, imagine how freaked out the average user is)”.
Privacy is important for quality of life. People leading more interesting/complicated lives than I do and people trapped in abusive power relations (corporate, domestic or otherwise) cannot afford to use this type of software.
The software may be pre-installed on the rom, it may be baked into the baseband itself. The fact that it is present on cell phones, may lead to an implicit social practice it is impossible to opt out of without social ostracism. It can and does encroach more and more into our lives.
Questions and the pre-empting of them will lead to self-censorship and (self-)limitation of freedoms which used to exist. The possibility to create some leeway in your day to day obligations to make life more pleasant/tolerable will disappear.
Just try to figure out all the edge cases, the ambiguity, the risk and the potential for catastrophic error. This is not a solvable problem and I think we need a hard design principle here: Any location based social application needs to provide a way for transparent spoofing to prevent socio-technological tyranny.