Jeremy Zawodney writes

The News RSS Feeds are great if you want to follow a particular category of news. For example, you might want to read the latest Sports (RSS) or Entertainment (RSS) news in your aggregator. But what if you'd like an RSS News feed generated just for you? One based on a word or phrase that you could supply?
...
 For example, if you'd like to follow all the news that mentions Microsoft, you can do that. Just subscribe to this url. And if you want to find news that mentions Microsoft in a financial context, use Microsoft's stock ticker (MSFT) as the search parameter like this.

Compare this to how you'd programmatically do the same thing with Google using the Google Web API which utilizes SOAP & WSDL. Depending on whether you have the right toolkit or not, the Google Web API ease either much simpler or much harder to program against than the Yahoo RSS based search. With the Yahoo RSS based search, a programmer has to directly deal with HTTP and XML when programming against it while with the Google API and the appropriate XML Web Service tools this is all hidden behind the scenes and for the most part the developer programs directly against objects that represent the Google API without dealing directly with XML or HTTP. For example, see this example of talking to the Google API from PHP. Without using appropriate XML Web Service tools, the Google API is more complex to program against than the Yahoo RSS search because one now has to deal with sending and receiving SOAP requests not just regular HTTP GETs. However there are a number of freely available XML Web Service toolsets available so there should be no reason to program against the Google API directly.

This being said there are a number of benefits to the URI-based (i.e RESTful) search that Yahoo provides which comes from being a part of the Web architecture.

1. I can bookmark a Yahoo RSS search or send a link to it in an email. I can't do the same with an RPC-style SOAP API.
2. Intermediaries between my machine and Google are unlikely to cache the results of a search made via the Google API since it uses HTTP POST but could cache requests that use the Yahoo RSS-based  search since it uses HTTP GET.  This improves the scalability of the Yahoo RSS-based search without any explicit work from myself or Yahoo, this is just from utilizing the benefits of the Web architecture.

The above contrast of the differing techniques for returning search results as XML used by Yahoo and Google is a good way to compare and contrast RESTful XML Web Services to RPC-based XML Web Services and understand why some people believe strongly [perhaps too strongly] that XML Web Services should be RESTful not RPC-based.

By the way, I noticed that Adam Bosworth is trying to come to grips with REST which should lead to some interesting discussion for those who are interested in the RESTful XML Web Services vs. RPC-based XML Web Services debate.