A few thoughts
From what we hear across the pond, crime rates (particularly rates of violent crime) in urban and semi-urban areas of Britain are achieving truly impressive levels of frequency amongst a population largely barred from any effective defense of their homes and persons against such depredations - routinely surpassing efforts of bad actors on our shores (at least those not currently elected to Congress) in daring, brutality, and frequency.
This is despite apparently vast depredations against subjects privacy (in terms of reported near-universal camera placement) to minimal good effect. Regrettably, it seems a universal that "monitoring" is much less useful to victims (and those proposed for the honor), than timely intervention by authorities, surrounding persons, or victims themselves, acting in rational self-defense against such offenses whilst still in progress - by preference, rather early...before the victim takes serious injury.
Considering the above, the eruption of various for-profit or NGO private efforts absent effective government action is less than utterly surprising - a symptom of under-funded, ill-trained, or politically emasculated (or some combination thereof) law enforcement, adjudicative, and correctional mechanisms.
I'm not heaping praise upon the site, but rather suggesting that it is a sign that both authorities and the more liberal/progressive citizenry awake to the notion that whatever they are currently doing about crime is working so badly that folks are starting to think in terms of extralegal action.