Memory products are "speed binned" before sale. This is a process by which the modules are tested to find out the highest stable speed at which each can operate, and then marked appropriately. Of course, if all memory is validated by the chip manufacturer, why not simply trust them?
Well, besides going directly from fabricators to module producers, RAM is also traded as a commodity on the open market. We've seen what happened when "commodity grade" capacitor failures brought down motherboard manufacturers, so what is to prevent an unscrupulous RAM producer from adding a low grade component to the mix?
Another problem that rears its ugly head is remarked RAM. These are modules that are advertised as being capable of operating at a higher speed than that for which their chips have been validated. In the most severe cases, chips have had their IDs scrubbed off and remarked, and are then sold as higher speed versions. Even easier for counterfeiters is RAM that's simply relabeled with a sticker.
Counterfeit RAM? Unfortunately, it happens. Counterfeit memory most often enters the market through discount vendors in fly-by-night operations. Warranties offer buyers some assurance, but how much is a warranty worth when the company backing it disappears?
Above and beyond the obvious counterfeit operations are larger-scale module assemblers that produce a cut-rate product using legitimate parts but low-quality production methods. Poor quality solder joints can degrade over time; the manufacturers often know this, so many of these parts carry an abbreviated warranty. Such products often cause random errors during that warranty period, but with low enough frequency that purchasers don't suspect a hardware defect as the culprit.
Why risk data corruption with cut-rate parts that you'll probably need to replace anyway? We recommend using brand-name products with a lifetime warranty - and a reputation that stands behind it.