Add more disadvantages of REST (donnemartin#9)

Author: yangshun

README.md

@@ -1458,6 +1458,8 @@ REST is focused on exposing data.  It minimizes the coupling between client/serv
 
 * With REST being focused on exposing data, it might not be a good fit if resources are not naturally organized or accessed in a simple hierarchy.  For example, returning all updated records from the past hour matching a particular set of events is not easily expressed as a path.  With REST, it is likely to be implemented with a combination of URI path, query parameters, and possibly the request body.
 * REST typically relies on a few verbs (GET, POST, PUT, DELETE, and PATCH) which sometimes doesn't fit your use case.  For example, moving expired documents to the archive folder might not cleanly fit within these verbs.
+* Fetching complicated resources with nested hierarchies requires multiple round trips between the client and server to render single views, e.g. fetching content of a blog entry and the comments on that entry. For mobile applications operating in variable network conditions, these multiple roundtrips are highly undesirable.
+* Over time, more fields might be added to an API response and older clients will receive all new data fields, even those that they do not need, as a result, it bloats the payload size and leads to larger latencies.
 
 ### RPC and REST calls comparison