I think what MM was trying to say is that though Excel and Numbers are both spreadsheet programs they take different approaches to implementing the concept of a spreadsheet into a user interface. Excel follows a more traditional (VisiCalc, Lotus 123, Quattro Pro) approach in which formatting data takes a back seat to manipulating numeric data through functions. Numbers places much more emphasis on format while lacking many of the more advanced functions of Excel. In some ways Numbers is more of a table program than a spreadsheet program.
There may be an option in Excel Preferences to limit the spreadsheets size, but I don't have Office 2011 on this computer, so I can say for sure. The other possibility would be to limit the size using VBA.
One way to visually simulate a limited number of rows and columns would be to select the entire sheet, give it a background color, and remove its borders. Then go back and selet the rows and columns you want to show and remove the background color and add the borders back in. I say visually because it will look like a smaller sheet but it will still function like a 10,000 column spreadsheet.
Can't help you on the not enough memory issue.