They make little gasoline engines that can be added to bikes, and it's not uncommon to see those added to $100 mountain bikes. So you get cheap bike, novice rider, and excessive speed to contend with.
On the plus side, I see more ads for those things than I do the actual bikes with them- saw one the other day, for about the first time in 5 years- but they're always being sold somewhere.
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"be careful this rando stuff is addictive and dan's the 'pusher'."