Aware that touched on other areas, but for one a system of continuous recording is unnecessary as one wants to be alerted and record the event. If one wanted continuous recording then one would have opted for a different system.
A system of increased recording times would be nice, so if you record 30 seconds of the first movement sensed, but it senses movement within (x ) - Time frame of first trigger event, then recording length up's to say 1Min, and again if trigger within X then double recording time is 2 minutes, etc. That way it covers enough time to catch event, and allows people enough recording time to make some difference. Offers enough recording time to makes a difference, but stops wasted bandwith with recorded unwanted time frames.
You could offer to allow viewers the option to record footage via the web-app just use a screen grab and record to a paid cloud service. Just a thought.