It's not that strange. Like any company that's serious about using the net and social media these days, they probably have a very simple custom search programmed on Google to look for references to their company so that their PR can follow up immediately.
No, it isn't. Spam is when you get unwanted or irrelevant e-mail or posts. If someone asks a question about a company, and the company responds, that's perfectly okay, surely? However, if the original poster had been paid to post the thread or question, which is always possible (a lot of companies and indeed nation-states* pay chat forum members to post on their behalf), then the whole thing is spam. (*The Chinese government is a very good example...)