Earlier quoted context omitted.
There are several problems with it: 1. the certificate is not generated by you (in the Free or the Pro plan) but by them and these certificates are for multiple domain names. So you end up sharing your certificate with other domains / websites of dubious nature that are also on CloudFlare's network. 2. CloudFlare only secures the connection between users and the CloudFlare network. It does not secure the connection b…
Why is #1 an issue?
Don't know what the implications for that are, except that someone poking around the validity of my SSL certificate will establish that mine is a free tier Cloudflare one.