Historically, some of the big problems of running UDP-based services over the internet are related to source spoofing, used in reflection/amplification attacks

Historically, some of the big problems of running UDP-based services over the internet are related to source spoofing, used in reflection/amplification attacks etc (looking at you, DNS/NTP), which is possible as very few providers carry out source address validation on egress. Looks like QUIC has a nice solution to this, making the impact of source spoofing similar to that of TCP, give or take a few CPU cycles: https://jacobianengineering.com/blog/2016/11/1543/ https://jacobianengineering.com/blog/2016/11/1543/