Also, if you ever lose control of a namecoin domain you can say goodbye to it forever. A squatter will take it instantly and hold on to it forever unless you buy it from them for actual money.
Has squatting gotten worse on Namecoin? Squatting is fairly hard to handle in decentralized naming systems in general. Namecoin got a lot of squatting issues mostly because of the pricing function (price of names dropped over x years, and now it's almost free to register names). Here is another paper from WEIS'15 that studied squatting in Namecoin: http://randomwalker.info/publications/namespaces.pdf
Depends on the toplevel suffix. For instance, .fr (France) domains have a "no taking" period after the expiration date, where nobody can take it from their previous owners. The owner can then take it back, but it won't be re-activated for a couple of weeks, I believe. So the punishment for screwing up is a temporary blackout of your domain name.
.com, .net, .org domains are handled differently, and may be easier to lose permanently.