Empty .getParam() does not return an array with dump() craft.request.getQuery() returns:

array (size=5)
  'tags' =&gt; string 'anxiety' (length=7)
  'maxPrice' =&gt; string '' (length=0)
  'sessions' =&gt; 
    array (size=4)
      0 =&gt; string 'email' (length=5)
      1 =&gt; string 'chat' (length=4)
      2 =&gt; string 'skype' (length=5)
      3 =&gt; string 'phone' (length=5)
  'hours' =&gt; 
    array (size=3)
      0 =&gt; string 'office' (length=6)
      1 =&gt; string 'evenings' (length=8)
      2 =&gt; string 'weekends' (length=8)


Whereas craft.request.getParam() throws an error:


  PHP warning
  
  Missing argument 1 for Craft\HttpRequestVariable::getParam(), called in /home/vagrant/Sites/counselling-anywhere/craft/app/vendor/twig/twig/lib/Twig/Template.php on line 609 and defined


This should have changed in Build #2465 right? I'm assuming it'll still work the same, but it's confusing that they don't return the same results.

Is this by design?
The behaviour you're seeing is by design – craft.request.getQuery() will return all GET variables if it's called without arguments, whereas craft.request.getParam() requires the name argument – i.e. craft.request.getParam('foo').

The changelog notes for build 1.3.2465 does reference a couple of issues related to these methods, but nothing suggesting any changes in regards to the required name argument for getParam(). Unfortunately, the GitHub repo for Craft builds doesn't go back as far as 1.3.2465, so I'm unable to verify this though.