Google can DDoS?

Google has "Search by image", which takes source image from supplied URL. And other sites, like vk.com, access any URL you supply them.

Can all these services be leveraged for DDoS purposes?

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What would stop Google from taking over the Internet?

For example, Google may replace each populat site one-by-one with their own alternatives or force you move your site into their cloud hosting (just because it is already there).