I see plenty of parked domains (equipped with Google Adsense ads) being promoted through Google Adwords. Means a domain owner is paying Google money to advertise a parking page with Adsense links, and when clicked on those, Google receives money the second time from the original advertiser.
This seems to be perfectly fine for Google (understandable ;-), thus I assume for parking companies it would be as fine as it is for Google.
Now since you are allowed to promote your parked domains with paid Google advertising, why should you not be allowed to promote your parked domains for free through your friends, family, your website or other means ?
However, if you promote or advertise your parked domain with the comment or teaser: "please click on the links on my page" or "click on my sponsor links" etc etc, then you are breaking the Google's Adsense rules and probably most parking company' rules as well.
just my 2 cents.....