From the voting T&Cs:
13. Four voting bundles will be available on the App Store; 12 votes for 69p, 35 votes for ÂĢ1.99, 50 votes for ÂĢ2.49 or 100 votes for ÂĢ4.99. You are limited to 500 votes per week (Monday to Sunday). |
That's from the iDevice section, although similar rules are in the Android and Facebook equivalents.
(taken from DS)