imo webhost.info would sound more authoritative. You are right that sometimes the s is better, and a logical choice for a webhost portal.
Its a toss. But eg. webcompany.info to me as a portal sounds just perfect imo - webagency.info, webconsultant.info. Dunno, sounds more authoritative than the plural version.
webbooks.info would be better than webbook.info. webjobs.info would be better than webjob.info
As a principle, however, I try to grab both the singular and plural
