They're fine, and legitimate. And once one gets put up, the future ones can get closed as duplicate. Asking for hosting recommendations is a tradition in web site discussion mailing lists that spans at a minimum 12 years. There's no reason Pro Webmasters can't do the same. If someone is making a recommendation purely based on a referral fee, downvote it. If the thing gets too karma-whorish, make it community wiki.
That said, a more specific hosting recommendation, like "I need Postgresql and nginx and ssh access, what shared hosts have this combination and are good?" are legitimate question. They might be good questions for ServerFault too, but that doesn't make it a bad question for Webmasters.
Worrying too much about what is and is not on-topic makes a forum less useful. The key is to trim away obvious sales pitches and encourage constructive help for the people who come seeking answers.