I don't give a stuff what they're intentionally doing, fact of the matter is last time I tried to download something from mediafire it tried to redirect to a drive-by downloader that was blocked by my antivirus.
I, and nearly everyone else, stopping using mediafire because of that issue. This is only the final nail in the coffin. Stop playing devil's advocate here, there's literally no reason to.
i mentioned this earlier, that's something mediafire let slip through.
the popup happens when you click anywhere on the page, it's a backdoor javascript put by one of the ads. in this case, mediafire should definitely address it because it's a threat to people's security
apart from that everything else is just fair game.