The thread centers on whether an MP4 stored on a flash drive can be shared with someone while preventing them from copying, transferring, or redistributing it. The main answer is that there’s no foolproof consumer-level way to “copy protect” a standard MP4 once the recipient can access and play it, since any readable file can be copied or captured; only managed/DRM-enabled environments or special setups can meaningfully limit distribution. Overall sentiment is pragmatic and cautionary, emphasizing tradeoffs (e.g., streaming, watermarking, encryption) rather than complete prevention.