Your sentences would appear to contradict each other.

Not really. Now advertisers can't play one platform off against the other. Now they'll just sell you ads across both platforms with better rates.

The "market" is the advertisers, so definitely a threat. One reason Facebook seems different is that it's more naturally social, but the truism remains: if you're not paying, you're not the customer. That WU pinned an ad-free account at $10/YEAR tells me TWC was likely not happy with them as competitors.

weatherspark.com That will surly suit your fancy

I concur, weatherspark is awesome. My only complaint is that the documentation is a little lacking for some of the advanced charts.

Does anyone know if NWS has a good API?

There are number of different ways to access the NWS data and graphs - not surprisingly it is hard to discover them! They do have an XML web service for daily and hourly forecasts http://graphical.weather.gov/xml/ but you can also download binary files that contain all the same weather elements for the US.

I'm actually close to completing a python library that will be open source and provide an easy way to access the NWS national digital forecast database.

It's pretty good. Last time I looked (3-4 years ago), the hard part was getting decent radar data/images.

But competition is good.