[docs] feedback from PR159

docs/docs/guides/asynchronous-data-queries.md

@@ -156,7 +156,7 @@ The following example will render the current user's name and a list of their fr
 ```jsx
 const currentUserIDState = atom({
   key: 'CurrentUserID',
-  default: 1,
+  default: null,
 });
 
 const userInfoQuery = selectorFamily({

docs/docs/guides/asynchronous-state-sync.md

@@ -54,7 +54,7 @@ If you want to handle synchronization of multiple atoms in a single place, you c
 
 ## Bi-Directional Synching
 
-You can also sync the state so local changes are updated on the server:
+You can also sync the state so local changes are updated on the server.  Note that this is a simplified example, please take care to avoid feedback loops.
 
 ```jsx
 function CurrentUserIDSubscription() {
@@ -89,7 +89,7 @@ function CurrentUserIDSubscription() {
 
 ## Synching State with Parameters
 
-You can also use the [`atomFamily`](/docs/api-reference/utils/atomFamily) helper to sync local state based on parameters.
+You can also use the [`atomFamily`](/docs/api-reference/utils/atomFamily) helper to sync local state based on parameters.  Note that each call of this example hook will create a subsription, so take care to avoid redundant usage.
 
 ```jsx
 const friendStatusState = atomFamily({