Standalone farm is targeted to development and testing environment so avoid to used it in production site for the following reasons:
- Can't Scale : you cannot extend your farm by adding new server if it configured as standalone farm even you can't backup the farm and restore it from standalone farm to multiple servers farm (Small , Medium,.. Farm) and vice and versa.
- Limit Storage: because it configured with SQL Server 2008 R2 SP 1 Express version your storage limit to 10 GB only for each database.
- No Domain Service: because it configured in one server only so no Domain Service or domain accounts and it run under local accounts like Network Service account. also you can not create User Profile Service for this reason.