.357Mag K frames have a documented tendency to split the forcing cone at the 6 o'clock position when subjected to heavy use with full-power Magnum loads using
lightweight bullets. However, this issue is like the .40S&W Glock kB! issue in that many panicky folks on the 'Net have arguably exaggerated the problem. Many, many .357Mag K frames have fired thousands of rounds without this problem. A good pre-purchase inspection is in order, but if the gun checks out OK, it's more of a "take appropriate precautions" issue (like the Glock kB! thing) rather than a "gun may blow up in your hand with any given shot" issue (like the early Airweight aluminum cylinder).
.22LR Smiths made prior to about 1935 lack countersunk chambers that enclose the case head. This makes manual extraction impossible if a case head separation occurs. Post-1935 models enclose the case head and reduce the chances of a total head separation. (That said, .22LR case head failures are far less common with ammo made today than the ammo made before 1935!)
Recently-manufactured Model 67's made with a two-piece barrel, which consists of an inner liner and an outer shroud, have suffered a number of well-documented instances of the barrel catastrophically breaking off and flying downrange upon firing.
S&W recently reverted to the older-style 1-piece design, although AFAIK they have not officially acknowledged the problem, and a number of J, L, and N frame models with similar 2-piece barrels curiously do not seem to have suffered from this problem at nearly the same rate. However, not many M67's have been sold with this type of barrel, due to the lessening popularity of full-size .38Spl revolvers.