What software packages are used to host and manage online personals
websites (i.e. Yahoo! Personals, match.com, etc.)  What types of
databases are used? Have each of these sites been built independently
or do they use a more standardized bundle of programs?  What company
provides this software for the large sites? (OR - Who is developing it
for them?)

Do these companies typically host their own sites, or are they hosted
elsewhere?  What would be the pros and cons of each?

Online personals Web sites could be developed on a number of different
platforms and in a number of different ways.

Portal software, such as IBM's WebSphere Portal or BEA's Weblogic
Portal, provide powerful API's and some out-of-the-box components
(portlets/widgets) that would be necessary for such a site. For
example - the first thing you need is Personalization. Portal software
provides Personalization features (i.e. ability to register users,
create user profiles, easily add any number of custom attributes to
user profiles, etc). In addition, the portal platforms provide the
authentication mechanisms for logging in. Once a user is logged in,
they can customize their view by adding or removing portlets. Or, the
view will be dynamically customized based on rules, roles, or
entitlements. Both of the platforms mentioned provide all these
features. So, while one could create a "home-grown" solution, it would
be more preferrable to build one on top of a portal platform such as
one of the two mentioned here.

These portal platforms usually can utilize any preferred database on
the back-end such as IBM's DB2, Oracle, or Microsoft SQL. A home-grown
solution might even utilize an open source database such as MySQL or
Postgre.

Many of these companies hire a consulting organization if the project
is relatively large and complex. Companies like IBM (or other
technology consulting firms) can provide the Project Management,
Technical Architecture, and Development skills required to complete
such a task.

Usually, a large site would be hosted outside of the company itself by
a hosting facility like DataPipe. These types of facilities provide
the bandwidth, server rack space, and various other services (such as
site security [some of the places are literally bomb-proof], data
back-up, deployment services, etc.). The pros of hosting in such a
facility are simple - leave the hosting up to people who know hosting
- while focusing on the business of developing the site and managing
the business. A service level agreement assures an up-time percentage.
The cons of doing it yourself, of course, is that it is not simple -
and time spent doing such is taken away from the time you can spent
managing the business and the site itself.