The most unsettling thing about the wealth of information gathered across Google as shown within the new My Activity dashboard is the unfortunate limit of human memory; as I drilled down into my online past I found every single voice search sitting there ready to be replayed alongside every video I've ever watched on YouTube. These are digital artefacts that we often forget about, instead focusing on past web searches or email accounts. My Activity is not, however, a harbinger of "Google is evil"; it introduces a bit more control over your data. I've had most of these searches paused for the last few months (so they don't inform future searches) and it's possible to delete them forever.
My Activity is beneficial in that it allows you to control the kinds of targeted ads that Google serves you: flip a switch and turn off targeted Google Search Ads based on your interests (signed-in ads) and also signed-out ads beyond Google.com if you wish. Before you switch these off, click through to take a look at what Google does base targeted ads upon because it shines a spotlight on the wide variety of data that informs ads including a timeline of your movements across Google Maps.
