Netflix's speed rankings show that video streaming performance on Verizon and Comcast has been dropping for the past three to four months.
The rankings were updated this morning with data from January. Verizon FiOS dropped from sixth to seventh best in the US, swapping places with Time Warner Cable. Comcast stayed in 14th place out of 17 rated providers, while Verizon DSL dropped from 16th to 17th, trading places with Clearwire.

The story is really in how each provider's megabits per second changed from month to month. Verizon FiOS suffered just a tiny drop from 2.22Mbps to 2.2Mbps from October to November, but then it went down to 2.11Mbps in December and 1.82Mbps in January.
(Note that if you want to see a graph containing all ISPs, or get different data sets, check out this Netflix link. The charts in this story were generated using Netflix's tool, which rearranges the values in the y-axis depending on the data being presented. Make sure to check the Mbps numbers in the y-axis when examining each chart.)

Verizon DSL dropped for four straight months from 1.42Mbps to 0.97Mbps, with the largest single-month drop occurring between December and January.
Comcast also dropped for four straight months, from 2.11Mbps in September to 1.51Mbps in January.

Verizon customers have been complaining about poor Netflix performance lately, so the numbers aren't necessarily a surprise. Determining the actual cause of such performance slowdowns is never easy, though. That the latest performance complaints came after Verizon's win over the FCC in a court battle over net neutrality rules led to claims that Verizon was celebrating its victory by throttling Netflix traffic.One such claim was backed by some traceroutes and a quote from a hapless customer service representative, but we explained last week why that wasn't enough evidence to declare that Verizon is suddenly throttling Netflix as a result of the net neutrality ruling.
Still, that doesn't mean Verizon isn't taking steps that degrade Netflix performance. If anything, the Netflix data shows that Verizon's performance problems started before it got the net neutrality rules overturned. And Verizon and Comcast have each garnered their share of Netflix-related complaints for months, if not years.