The lesson for the marketing practitioner is simple: Diligent proofreading is de rigeur for all media.
Why? Because more people are likely to see your firm's Facebook and Twitter postings than your data sheets, so making the mistake of dashing off a Tweet on the fly can potentially cost you more than reprinting those brochures. Treat your posts with the same care you do your sales presentations. After all, you don't want to end up featured in a rogues' gallery like "Best Obnoxious Responses ..."