Is there any difference between the Web Edition and Business Edition of Azure SQL Database other than the maximum supported database sizes? I'm assuming the naming has some significance but all of the information I find simply talks about the max db size. I want to know if there are any other differences such as SLA, replication, scalability, etc.
Any clues?
The two editions are identical except for capacity. Both offer the same replication and SLA.
EDIT April 3, 2014 - Updated to reflect SQL Database size limit now at 500GB
EDIT June 17, 2013: Since I originally posted this answer, a few things have changed with pricing (but the sizing remains the only difference between web & business editions)
Web Edition scales to 5GB, whereas Business Edition scales to 500GB. Also: with the new MSDN plans (announced at TechEd 2013; see ScottGu's blog post for more details), you'll now get monthly monetary credits toward any services you want to apply your credits to, including SQL Database (up to $150 per month, depending on MSDN tier - see this page for details around the new MSDN benefits).
Both allow you to set maximum size, and both are billed on an amortized schedule, where your capacity is evaluated daily. Full pricing details are here. You'll see that the base pricing begins at $4.995 (up to 100MB), then jumps to $9.99 (up to 1GB), and then starts tiered pricing for additional GB's.
Regardless of edition, you have the exact same set of features - it's all about capacity limits. You can easily change maximum capacity, or even change edition, with T-SQL. For instance, you might start with a Web edition:
CREATE DATABASE Test (EDITION='WEB', MAXSIZE=1GB)
Your needs grow, so you bump up to 5GB:
ALTER DATABASE Test MODIFY (EDITION='WEB', MAXSIZE=5GB)
Now you need even more capacity, so you need to switch to one of the Business Edition tiers:
ALTER DATABASE Test MODIFY (EDITION='BUSINESS', MAXSIZE=10GB)
If you ever need to reduce your database size, that works just fine as well - just alter right back to Web edition:
ALTER DATABASE Test MODIFY (EDITION='WEB', MAXSIZE=5GB)