Why is “Spotlight Web Content” using so much VRAM and CPU? Why is “Spotlight Web Content” using so much (32.56 GB) virtual RAM and CPU (up to 122.41% apparently)? More interestingly, how can I prevent it from doing so?

I am running this MacBook Pro with 4GB RAM and OS X 10.10.2 Yosemite.

I found this in Acticvity Monitor when my Computer was close to not responding anymore and killing it solved that problem. It shows the process had quite a high number of errors, as well (27443815).
The Spotlight Web Content process is part of Spotlight Suggestions. When you start to type in Spotlight or the Safari address bar, Apple sends what you are typing out to their servers to suggest possible web matches and pre-fetch web pages based on what the system thinks you might be looking for.

For example, if you start to type N E, it may pre-load netflix.com.

As far as why it using so many resources, that's difficult to say. Is this the first time this has happened? It may have crashed. Keep an eye on it and see if the issue reoccurs.

You can also disable Spotlight Suggestions and that should stop this thread from appearing altogether.

Go to System Preferences > Spotlight and uncheck Spotlight Suggestions and Bing Web Searches. Then, in Safari, go to Preferences > Search and uncheck Include Spotlight Suggestions.