I regularly am discussing Google's business with Googlers on here. Some of them disclose in the post, some of them disclose on their HN profile. Many do not, and calling them on it is generally discouraged, but it's usually not super hard to figure out or prove.

There are definitely some acting as spokespeople (even if they claim otherwise), but there are also quite a few who are just, you know, incredibly biased fans of their employer, who like to defend them on topics unrelated to their job.

But when a tech company has 100,000 employees, it's not particularly surprising to see a good number of them on a tech forum. ;)