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Proper etiquette is to not do it, or at least do it very rarely. I would say the example you used about posting to your news feed when you had something published is different, because you are really sharing something that you accomplished. If you accomplish something personally, say a high profile new account or the like, I wouldn't have a problem with someone announcing that in their personal account, because, as in the above example, you are really sharing something that you accomplished. When you start using your personal account as a back door to get your corporate message out to people who have not expressed an interest in it crosses the line into advertising.
This technique of is also likely to be counterproductive and get the person "unfriended" or ignored. How effective is it going to be when you annoy everyone by treating their news feed as a corporate billboard? Not very. If I had to make a bright line rule, it would be this: If you are sharing your own professional accomplishments, that's ok. If you are pimping for you company, that is not.