Does Facebook have limits on the number of wall posts a fanpage can post per day on other fanpages?
For instance, from my fanpage ( not my personal page ) I went to a fanpage in my niche and posted a picture on their wall and it showed up in "Recent Posts by Others" which was great.
I then went to a different fanpage in my niche and posted a picture to their wall, this time it did not show up under "Recent Posts by Others", it showed up in their "Photo" page, which is not good, because of course not as many people will see it.
A Page can be a person, a persona, or a company/business. I haven't encountered limits that I know of in this sense. When I comment as my Page on another Page, that's similar to the interaction individual accounts might have with one another. It's communication among fans/subscribers.
Ads get out to an entirely different set of users who might not otherwise know of your Page. There's still plenty of incentive to use them.