Do large corporations and product companies follow any standard quality models/processes at all? For example, I have seen that many large organizations have proprietary processes in IT and software development. Back in the days (even before Motorola's Iridium project,) I remember many IT companies scampering for SEI-CMM certification. Do any of the Fortune 500 company try to adopt these quality processes? In my limited experience I have not seen them undergoing audits for adherence to processes. Most of the audits are either financial, or issues pertaining to legalities.Am I just being ignorant, or is this true? If true, how stringently do the companies adhere to the processes? 
ISO, Six Sigma, SEI-CMM, etc., in Fortune 500 companies
development process;quality;methodology
In the telecom domain, almost all of the tier 1 vendors have ISO 9001 (for quality) certification and  TL9000 (telecom industry specific guidelines). If you want to compete in the European market, some sort of certification is a must. US and Japan do not care much for processes. This is specific for the carrier class (service provider) telecom equipment market.Personally I feel quality processes are just eye wash. Most people dress up documents just before the audits. Auditors find enough discrepancies to keep them in business while still awarding the certification. It is impossible to audit an year's worth of work done by 100 people by 1 person in a week (assuming 100:1 ratio for engineers:auditors).During the rest of the year, people are more focussed on the product than on the process. Process are necessary for any company to scale and have minimum standards across the company. But ISO processes do not mandate quality processes. It is up to each individual company what process they are going to follow. ISO just audits if the company sticks to it or not.I do not have personal experience with CMMI processes. But it is kind of a big deal here in India. A lot of companies are CMMI-level 5 certified. This is mostly to win more clients to outsource to them. I do not think CMMI level 5 is any indicator to quality of work produced by a company.