Plenty of people are cybersquatting, often out of ignorance and without any malicious intentions.
Just because they are, doesn't seem they are safe, and that it's safe to follow their example.
More to the point, why do you think this domain has value, why would someone want to buy your domains in particular and not just pick another available domain ?
I take it as a given that the domains would have low resale value for domainers, noting the response so far in this thread. Presumably this is due to the perceived risk of losing the domain under the Anti-Cybersquatting and Protection Act, or other trademark infringement action.
As for whether it would be legitimate to actually use these domains for a site providing unofficial facebook commentary, this is an entirely different question. To the extent that they could be used legitimately, then there could be some value in the names (due to brand-ability and keyword match), just not for those who would only buy for the purpose of selling at a profit (due to the anti-cybersquatting laws).
In terms of what uses of a domain that contains a trademark might actually be legitimate (eg fair comment) versus illegitimate (buying just for resale at a profit), see the analysis and cases referred to here:
hxxp://en.wikipedia.org/wiki/Anticybersquatting_Consumer_Protection_Act
To give a real world example, allfacebook.com and insidefacebook.com are active sites providing facebook commentary. They seem to be maintained by WebMediaBrands Inc, which is a publicly listed company. While it appears that they may fall within the 'fair comment' usage of the trademark, it is quite possible that Facebook has simply not elected to enforce their rights in respect of these domain names (for whatever reason).
I will be - but mainly because I've moved on to other projects and can't be bothered developing the sites I originally envisaged.
Part of my reason for keeping posting on this appraisal thread was to try and understand the reasoning why including a trademark in a domain name is such a bad thing - in order to understand where the advice was coming from.
Anyway, that's probably enough from me for now. Thanks for the replies - much appreciated.