These are some ideas of what we might measure.
Product...
- sign-up/in experience (i.e. account requirements & communications, including frequency of email/calltoaction communication)
- general functionality & features
- customization of editing tools (i.e. pick your color/font vs locked in choices, etc)
- sharing features
- community options, requirements
- publishing of tacks, smokes, checkthis's, etc on their own site — how is it done (auto vs curated), how are they tagged, categorized, presented, etc
- public vs private rules
- general language — how are they describing themselves
- what is the experience like on mobile browsers
Mindshare...
- possibly consider tracking news on key competitors (though I believe onsite & user interations/communications is really the key area of focus)
- identify & understand anything (especially built in dynamics) which force or facilitate viral sharing
- uptake, size of the community