So, you mean, small-scale squatters are okay; large-scale squatters are not?
The person owns the domain, they can do with it as they please. So if they want to rent it out, then they can ask money for it... It's your choice if you agree to their terms and make any exchange.
You do not own a domain. That is false right off the bat. And no, you cannot do with it as you please. For example, buying a trademarked name and then trying to extort money out of the owner of said trademark is not allowed.
If you are renting a domain with the sole intent to deprive someone else the ability to use it unless they pay an extortionist fee, that is wrong. It goes against the free spirit that the internet was built on. The fee charged is at least in part to prevent a massive "land grab" of domains that are to be sold off at absurd prices.
I've had experiences in the past of letting a domain expire and then being "ready" to use it a few years down the line. Of course, it was invariably squatted, and had been since I'd let it go, and would cost more than I was able to justify paying to get it back.
On the other hand, I actually had a working project running on wishmash.com that wasn't getting enough traffic to make it worthwhile, so I sold the domain when I got a reasonable offer. If I hadn't sold it, though, would that have have been "squatting is squatting is squatting" as well? I could put up forums and/or tiny sites on all domains I have -- then it wouldn't be squatting either?
There's a whole range of possible levels of domain usage. I don't have any domain that I haven't spend at least a few hours researching the space & competitors, documenting implementation (and sometimes starting it), and so on.
I'm sure I won't actually build some of these projects. But I don't know which. Of course from the outside this can look the same as a simple squatter hoping for a big payout; but that doesn't mean it is the same.
That is what makes you not a squatter. If you were trying to squeeze thousands of dollars out of those domains? yeah, I'd call you a squatter.
Actually no.
The closest true definition I [1] can come up with for "squatting" [2] would be defined as such (from wikipedia):
--------------
"Cybersquatting (also known as domain squatting), according to the United States federal law known as the Anticybersquatting Consumer Protection Act, is registering, trafficking in, or using a domain name with bad faith intent to profit from the goodwill of a trademark belonging to someone else. The cybersquatter then offers to sell the domain to the person or company who owns a trademark contained within the name at an inflated price."
--------------
So to clear up any misconception there is no problem registering a domain that a) you don't intend to use or b) you plan to sell or c) being in the business of buying and selling domains as long as you don't break any existing laws around trademarks (as only one example). Of course there are also issues with UDRP's and law firms reverse hijacking domains but that's an entirely different subject.
Lastly of course people who can't get the domain they want always will throw around the "c" word as if it's simply not fair that they can't have what they want when they want it. In a similar vein people are also opposing legitimate real estate and other property transactions if it personally effects them.
[1] I operate an ICANN registrar and I've been in this business since 1996. I've been quoted in the NY Times on domains and many other places. I'm one of the people asked about this type of thing and consult on the subject.
I still think it's squatting if I registered yoursurname.com, even though it's not a trademark and wouldn't meet your definition under the ACPA.
I still think it's squatting if I have no intention of ragging you in to buying yoursurname.com from me. Maybe I just derive satisfaction from having something you want?