Heroku, GAE and other SaSS are great, if and only if they have everything you need. For my own purposes, most of the things that I do now involves PostGIS which mean I have to use a PostgreSQL server. The cheapest option for PostgreSQL on Heroku starts at $200. That's just way out of my budget for now. I'd love to know how people do GeoSpatial searches and other GIS stuff using MySQL or other NoSQL solutions.