Feature comparison grids come in two forms:
comparing a company's own offerings with themselves
comparing a company's offering with someone else's offerings
Here's a grid comparing Drupal starter themes: http://triglobal.nl/do/drupal6starterthemes.html
How do these normally get created? For the web, using straight up table HTML. Not that there's anything wrong with that, but it's tedious work.
How do these get updated? How does one collaborate on a grid?
Maybe this exists already, but here's what I envision for a web app:
a wizard to get started quickly
each grid has its own ID
each offering goes on the horizontal axis
each feature goes on the vertical axis
each feature has a field type
each feature gets notes, since it's not always black and white
each grid is embeddable as a widget, so that if you change it on the web app, it gets changed everywhere
each grid exports stripped down HTML with sensible CSS IDs and classes for copy & pasting then later CSS/JS manipulation
the app can host a "landing page", which you can CNAME your subdomain to, with some ability to change colour and drop in an image or two, but that's it. One or two "themes".
drag and drop columns to set some offering against another
drag and drop rows to set features against each other
a short URL to share via the condensed text social networks
sensible "long" URLs