I have seen a proliferation recently of ads (especially in personals
listings) that say something like: "Want to chat? Just text <some
word> to 22428" (for an example, see:
http://zingy.com/operatorChat.php).  I know there must be fees
associated with this, but I can't find any information, anywhere.  How
does this work?  I'd love to know any or all of the following: does
one company own the "22428" text message number?  Is it owned by the
mobile providers (Sprint, Verizon, Cingular)?  Are there other
numbers?  Do they all cost money?  Who sets the price?  How do you
find out what the price is?  Any links to articles about how this
works on a technical or business level?

I'm amazed that they could get people to do this without disclosing
the cost. Is this just an extension of the telephone 900 system? 
Guidance would be great.

If you study that site you provided a little more you will have all
your questions answered. To find out what Zingy SMS is and to find out
how you download using SMS see
http://zingy.custhelp.com/cgi-bin/zingy.cfg/php/enduser/std_adp.php?p_faqid=454&p_created=1124296230&p_sid=EjAwEmSh&p_lva=&p_sp=cF9zcmNoPSZwX3NvcnRfYnk9JnBfZ3JpZHNvcnQ9JnBfcm93X2NudD0zOSZwX3Byb2RzPSZwX2NhdHM9JnBfcHY9JnBfY3Y9JnBfc2VhcmNoX3R5cGU9YW5zd2Vycy5zZWFyY2hfbmwmcF9wYWdlPTE*&p_li=&p_topview=1
These companies can be used for SMS messaging: Cingular, T-Mobile,
Nextel, Boost Mobile, Verizon Wireless Puerto Rico, Autel, Virgin
Mobile. Go to http://www.zingy.com/phonecompatibility.php

There are other numbers for downloading music, wallpaper, games, quizzes etc. 

Zingy is not owned by all these companies. Zingy is more like a vendor
to these companies.

For questions concerning the price of these features contact customer
service. Go to http://www.zingy.com/contactUs.php

You can find free SMS messaging by tying that into the search engine.
There are sonsered links to this message as well.

US Cellnet appears to own the 22428 SMS service.  


I think that this webpage has the answer you were looking for:
http://www.cellnetinfo.com/index.php?pi=apps.htm


US Cellnet apparently leases access to this number, and several
others, to 3rd party content providers (such as the person who placed
the personal ad looking to "chat" with someone).  Code 22428 is used
for SMS Operator Chat (OPCHAT), a service allowing users to
communicate with live operators employed by the service provider for a
fee (eg. advice lines, live psychics).  There are other codes which
allow a service provider to offer horoscopes and jokes, ringtones,
graphics, and micro-billing services.  Adult services are supposedly
prohibited, though I doubt that they can, or even would want to,
police them very diligently.


The schedule of fees that US Cellnet allows providers to charge their
customers is at: http://www.cellnetinfo.com/index.php?pi=rates.htm


It appears that a Chat SMS is $0.99 per message.

Remember, these are not telephone services, so they are not regulated
in the same manner as 900 lines.