fixes to tag alias cache expiration, improved instructions for sign up

app/views/users/new.html.erb

@@ -3,6 +3,10 @@
     <h1>Sign Up</h1>
 
     <p>A basic account is <strong>free</strong> and lets you keep favorites, upload artwork, and write comments. If you want <%= link_to "more features", wiki_pages_path(:title => "help:accounts") %> you can upgrade your account later.</p>
+    
+    <h1 style="margin-bottom: 1em;">This site is open to web crawlers so whatever name you choose will be public!</h1>
+    
+    <p>This includes favorites, uploads, and comments. Almost everything is public. So don't choose a name you don't want to be associated with.</p>
 
     <div id="p3">
       <%= simple_form_for(@user) do |f| %>