50 million, if that's what the article says.
It's really just a question of performance and scalability, but if the client really needs a quarter million items in a list, he'll have to accept a little waiting time.
Read this, where it says that SQL Server escalates to a full table lock if you exceed 5000 items. That means that you're probably going to be making other people wait, if they also require access to the same table at the same time.
Use the smallest possible threshold that will satisfy the client. Warn him that there may be performance penalties.