The Anarchangel takes on the fallacy of downloading magazines, and notes the two main exceptions: AR15 and Glock magazines. I can definitely concur on both of those (the only feed failures I ever had with my personally-owned Glocks, other than my G30's strong dislike for semiwadcutters, were caused by topping up full mags after chambering the first round.)
Add to the list the famous Wilson 47D eight round mag for the 1911. The combination of follower design and tube length will cause the spring to die a premature death if left loaded to its full eight-round capacity for any great length of time. Some folks rotate their mags; after several rebuilds, I just started using my 47Ds as seven rounders and haven't had to replace a spring for five years (although I probably should do so soon, if only on general principle)...
Let me add some tips for what to do with damaged mags, such as AR mags with spread feed lips or AK mags with feed-disrupting internal burrs: When I'm engaged in a practice session and I encounter a mag with issues, I set it aside in a pile. At the end of the session, I relocate the pile to the nearest trash receptacle after pounding the defective mags flat with a hammer, lest some penny-pinching fool rescue them in an attempt to potentially risk his life in the name of saving a few bucks. I consider it a public service.
(H/T to Unc.)