This patch is to allow empty strings or other objects that would be type casted to 'false' to be valid identifiers.
Index: dojo-release-1.3.2-src/dojox/data/jsonPathStore.js
===================================================================
--- dojo-release-1.3.2-src.orig/dojox/data/jsonPathStore.js	2009-09-04 11:21:12.000000000 -0700
+++ dojo-release-1.3.2-src/dojox/data/jsonPathStore.js	2009-09-04 11:22:20.000000000 -0700
@@ -541,14 +541,14 @@
 				this._updateMeta(item,{path: results[i].path});
 
 				//if autoIdentity and no id, generate one and add it to the item
-				if(this.autoIdentity && !item[this.idAttribute]){
+				if(this.autoIdentity && item[this.idAttribute] === undefined){
 					var newId = this.autoIdPrefix + this._autoId++;
 					item[this.idAttribute]=newId;
 					item[this.metaLabel].autoId=true;
 				}
 
 				//add item to the item index if appropriate
-				if(item[this.idAttribute]){this.index[item[this.idAttribute]]=item}
+				if(item[this.idAttribute] !== undefined){this.index[item[this.idAttribute]]=item}
 				count++;
 				tmp.push(item);
 			}