No, you can still have memory leaks with ARC. In practice, the GC Apple was using prior to ARC could collect cycles, but it consumed a nontrivial number of CPU

No, you can still have memory leaks with ARC. In practice, the GC Apple was using prior to ARC could collect cycles, but it consumed a nontrivial number of CPU cycles compared to ARC. Apple's tools people seem to be unconvinced that GC is efficient enough for production use on slow CPUs.