[inopinatus]

They're trying to drive up their volumes in the hope of obtaining more peering.

This is evidently the core of Cloudflare's business strategy, emerging in practically everything they do tactically; from Matthew Prince having an epic public sook earlier this year about AWS's network team telling him to jump in a lake, to this. Peering drives down the marginal cost of bandwidth, and this is super relevant since Cloudflare's main value-add product is DDoS mitigation. Unless you're an incumbent tier 1 carrier (which is the hereditary royalty of networking), the classic ways to obtain more/better peering are either have the most eyeballs, or the most content. A typical access ISP takes the former approach, a CDN like Cloudflare takes the latter.

As usual, free anything means you are the commodity being traded on.

[babelfish]

Source on the lake thing?

[inopinatus]

Not a literal lake, that's just a colourful metaphor for being rebuffed.

The fact of it is evident from the Cloudflare blog, but I don't particularly recommend giving that the time of day, since as with all content marketing it is also self-serving humbug.