There aren't any rules that say you cannot write a hub about online the surveys. Though you play hell trying to produce a hub worthy hub about them. The trick is to actually write something informative that people can learn from, and not to just produce another article trying to get people to sign up for online surveys. You'll also want to avoid doing the same old "how to make money online" scheme, cause it's been done to many times.
Online surveys aren't banned, but over commercialism is pretty much a no-no. Hubpages wants original content that people want to read, and no one wants to read another hub about signing up for surveys.