Ms. Smith seems to imply that the ONLY issue we should be paying attention to is cost.
If cab fares double when the number of cabs doubles, it will certainly be a negative for most consumers.
But there are also positives to be weighed. Example: Wait time. An hour wait for a cab is enraging. For many, it is the anticipation of this wait that causes them to chose an alternative means of transportation. (This undermines Smith's assertion that demand is static.) Shorter wait time will increase the likelihood that an individual will opt for a cab.
Another example: Customer Service. More competition will force the current cab drivers in Anchorage to provide better, friendlier customer service. This means pleasant attitudes, not talking on the phone during the fare, helping people with their luggage, and not driving like a maniac. Also, dispatchers with phone manners.
If Ms. Smith wants to convince me to vote Yes on 8, she needs to develop a stronger argument that addresses these issues.