That's actually not Verizon's policy. The activation charge is for establishing a new line of service. If you discontinued data use, and then restarted it, you should not be charged another activation fee since you would not be establishing a new line of service. This is how it has been done with the Galaxy Tab and iPad/MiFi. I have verified this with my Verizon rep, as well as Verizon customer service (see attached).
Best Buy is claiming multiple activation fees, because if you cancel the service within the first two months, they do not get their commission (aka bounty). They probably figure if they tell people that there are multiple activation fees, people won't figure out that they are lying until they've already received their bounty from Verizon.
Also, it's important to note that the activation fee and prorated data charges are refundable if you cancel the data service within 3 days.