If you're a heavy data user and still grandfathered in a Verizon 3G unlimited data plan, which the carrier recently replaced with tiered data plans, you could be facing throttled data speeds. Late last week, the carrier began throttling the top 5 percent of its heaviest-use 3G unlimited data customers.
Customers with a 4G LTE data plan or a 3G tiered data plan will not be affected. Hence, if you're still clinging on to the 3G unlimited data plan you picked up just months ago with the Verizon iPhone 4, the carrier's reps will be encouraging you to either switch to another device that supports 4G LTE, switch to a 3G tiered plan, or simply use more WiFi whenever you can.
Once you've crossed over the line, your speeds will be throttled for the remainder of the current billing cycle as well as for the next full billing cycle. However, Verizon insists that its throttling or "Network Optimization" is different from the practices of rivals such as AT&T and T-Mobile. Instead of throttling your data speeds entirely, you will only be throttled when you're in a congested cell site. So, depending on your location and your nearest cell tower, your data speeds may or may not be throttled.
The new policy took effect on September 15 and Verizon has posted a more detailed Data Disclosure page here.