YouTube, Facebook, and Twitter similarly struggle to moderate content, illustrating the larger issue of tech platforms swelling to a size where current guidelines for oversight are no longer adequate.

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Those items included: a children's toy xylophone with four times the lead allowed by the federal government, knockoff magnetic children's toys that can lead to internal damage if ingested, and a motorcycle helmet that was falsely listed as US Department of Transportation-certified.

Read more: Amazon was caught selling thousands of items that have been declared unsafe by federal agencies

"The challenge for Amazon is that what built the marketplace — it being so open and welcoming to new sellers — has also meant that today Amazon is really having a hard time enforcing many of its own rules, because it just physically cannot allocate enough human power to police many of these rules," Juozas Kaziukenas, an e-commerce analyst, told the Journal.

Here are the issues tech giants like Amazon, YouTube, Facebook, and Twitter are facing, and how they're attempting to regulate their platforms.