My thoughts:
- It it's on topic and they disclose that it's their own product, it's ok.
- If it's on topic and they don't disclose, I down-vote and ask them to disclose.
- If it's off-topic (even just a little), flag it as spam.
In an case these guys will be disappointed that all their links are marked 'no-follow' so search engines don't follow the links and score their pages higher; though users might still click through.