The biggest limitation is: You are limited by your provider's service.. you cannot use your phone where your provider does not have service (or with other companies they do not have a partership with).
As for someone elses answers:
(3) You can't also view the person you're speaking to. - video phones have been out for well over a year
(4) They can be very easily cloned. - GSM phones are difficult to clone
(5) There are too many different models on the market. - there are also a lot of cheap phones
(6) They're too expensive. - not if you're on the right plan
(8) You can't download full movies on them. - yeah you can... Blackberry Storm, iPhone for instance
(9) You can't watch tv on them. - Mobile TV has been available for many years with some providers
(10) You can't get that hot girl's digits without it. - you can use a pen and paper
As for someone elses answers:
(3) You can't also view the person you're speaking to. - video phones have been out for well over a year
(4) They can be very easily cloned. - GSM phones are difficult to clone
(5) There are too many different models on the market. - there are also a lot of cheap phones
(6) They're too expensive. - not if you're on the right plan
(8) You can't download full movies on them. - yeah you can... Blackberry Storm, iPhone for instance
(9) You can't watch tv on them. - Mobile TV has been available for many years with some providers
(10) You can't get that hot girl's digits without it. - you can use a pen and paper