The results are limited to 20 ( 40 for google ). Search radius depends on the location-based service you search in ( for Google is 5km, for Foursquare is 3km ...)
If you will use only search functionality, you can use operator "||" (OR) for multy search, but this works only for google.
Example : Instead of making two searches, one for KEYWORD and one for PHONE_NUMBER you can combinate them like that : KEYWORD || PHONE_NUMBER with maximum three terms.
Registered users can search by TYPE in Google. Let`s say you want to see top 40 dentist around entered address.
Example : type=dentist
Example 2 combination between types : type=dentist|establishment