The number games in this article are without any substance, especially the estimates for the percentage of upgraders. Other companies are using a tiered system

The number games in this article are without any substance, especially the estimates for the percentage of upgraders. Other companies are using a tiered system, where you get free lifetime upgrades for the base version and you pay a fee for premium/business services (Jungledisk.com is using this approach). This way you can build a (happy) userbase and increase the trust in the company. Satisfied customers are more likely to upgrade to a payed plan.