The "hostile" comments here are because (at least from my point of view):
1. PCGS has over the last few years been behaving with arrogance and a lack of understanding of collectors like you and I, and numismatics in general. They know they're #1 in the marketplace, and they feel like it's a license to take the
TPG process wherever they wish.
You want a
VAM attributed? It's gonna cost you
$24, even if you already know what the
VAM is. $24, just to have the
VAM number typed onto the label, and that's in addition to the highest grading prices in the
TPG business. Furthermore, they only attribute what they consider "significant" VAMs.
As a result, the first reaction of many collectors to this news, myself among them, is "What's in it for them?" PCGS is not known for doing things with altruistic motives.
Example: The
Morgan dollar entries are keyed to PCGS numbers - they have spaces only for the Morgan varieties they consider significant. There are 22 1878 7/8TF varieties; PCGS' wiki has spaces for two - "Weak" and "Strong."
2. Wikis are notorious for misinformation. When anybody can add content,
anybody does. And many "anybodys" know far less about coins than they think. One of our greatest foes here at CCF is misinformation; we're constantly having to correct possibly well-meaning but incorrect posts. Numismatics is nothing if not fact-intensive; check out the Peace/Morgan and US Variety forums if you don't believe me.

It's going to be a constant struggle for them to keep the information presented accurate. If they limit participation in the interest of accuracy, they defeat the purpose of a wiki and do nothing but siphon the efforts of dedicated people elsewhere.
3. They're duplicating existing work. Many highly-knowledgeable and motivated collectors are already compiling databases of the coins they specialize in. For example:
- Colonials: Go no farther than Notre Dame University's amazing compilation of colonial issues, endowed by Robert H. Gore, Jr.
http://www.coins.nd.edu/ColCoin/index.html- EAC, particularly Tom Deck. He has 234 of the 295 Sheldon varieties photographed on his website.
http://www.largecents.net/- Lincolns: Our own Coppercoins is one of the acknowledged leaders in the field of
Lincoln Cent study; you don't even need to leave CCF to get an authoritative opinion.
http://www.coppercoins.com/-
Two Cents: Our own nohope587, who owns enough of them to be measuring his collection as a percentage of the total mintage these days.

The Barber Coin Collector's Society. The Bust Half Nut Club. Gerry Fortin for
Seated coinage, especially dimes. VAMworld. Susan Headley's efforts at coins.about.com.
The information is already out there. You want to contribute? Get with the people who are doing this because it's what they love, not because they want to generate more foot traffic on their commercial site.