"SharePoint Server 2010 data is stored in SQL Server tables. To allow for the maximum number of possible columns in a SharePoint list, SharePoint Server will create several rows in the database when data will not fit on a single row. This is called row wrapping.
Each time that a row is wrapped in SQL Server, an additional query load is put on the server when that item is queried because a SQL join must be included in the query. To prevent too much load, by default a maximum of six SQL Server rows are allowed for a SharePoint item. This limit leads to a particular limitation on the number of columns of each type that can be included in a SharePoint list. The following table describes the limits for each column type.
The row wrapping parameter can be increased beyond six, but this may result in too much load on the server. Performance testing is recommended before exceeding this limit..."
$web = http://webapplication
$webapp = Get-spwebapplication $web
$webapp.MaxListItemRowStorage = 8 #the default value is 6