Is using SQL Express in a production environment a reasonable choice?
I looked at Microsoft\'s comparison chart:
http://www.microsoft.com/sql/prodinfo/featur
One thing to ask might be - if your needs outweigh the capabilities of SQL Server Express, will you be able to afford a commercial version?
I think the one of the ideas of SQL Server Express is that you could host your site on it and once you outgrow it (need more than 4GB, etc.) you will buy a commercial version, especially now that you're locked in to using it. But if your site will outgrow it sooner than the income coming in will be able to buy a commercial version, this could be a problem (and possibly a database design flaw if your site is consuming more data/disk space than it needs to)