I would be a bit worried if I had a small rabbit but in my experience, I've never had any problems with cats. All my buns have been medium-large sized so cats don't really pose too much of a threat. I only ever had one cat that would sit ontop of my aviary/run and just watch the bunnies underneath. I don't think the buns were too worried about it but I used a 'super-soaker' water pistol for a few days and the cat never came back :lol::lol:
I actually have more problems with a magpie at the moment. It's one of this years babies and it's developed an unhealthy interest in the rabbits. I've seen him peck them when they've been outside, although if the rabbits turn round to see what 'got' them, the magpie flies off. I think they see it more as an irritation rather than a threat.