AdMob sample code for Rails

I don't see any discussion about AdMob, an aggregator for ads for
mobile phones websites. They're going to live for a bit until AdSense
puts out it's mobile-capable versions.

AdMob just put up Rails sample code for Rails. I've included it below.
It's pretty simple. Unlike Google AdSense, which requires JavaScript,
this code builds an HTTP request, performs a GET from the AdMob server,
then gets the Ad text back that gets included in the HTML.

I've got a couple of questions and comments, hoping to have some other
sets of Rails eyes take a gander:

1) There are some obvious spots for refactoring. link_to isn't used,
for example. And a lot of this could be in helper functions.

2) That said, it seems like a bad idea to have all this embedded right
in the RHMTL template for performance. Is that right?

3) I don't understand the request.env lines. Will these get the IP &
the User Agent of the browser making the request? Will that still work
if it's in the RHTML? What about a helper function?

thx,
--dwf

<%
  require 'net/http'

  # editable area
  # change mob_mode from "test" to "live" when you are done testing
  mob_mode = "test"
  # use this to set a default link to appear if AdMob does not return
an ad
  mob_alternate_link = ""
  # end editable area

  # User agent and IP: used for ad targeting
  mob_ua = url_encode(request.env["HTTP_USER_AGENT"])
  mob_ip = url_encode(request.env["REMOTE_ADDR"])

  mob_m = ""
  if mob_mode == "test"
      mob_m = "&m"
  end

  # build the request url
  mob_url = "http://ads.admob.com/ad_source.php?s=[AdMobKey]&u=" +
mob_ua + "&i=" + mob_ip + mob_m

  begin
      # make the request
      response = Net::HTTP.get_response(URI.parse(mob_url))

      if response.code == '200'
          mob_content = response.body
          # parse result
          if mob_content.include?('><')
              mob_ad_text = mob_content.split('><')[0]
              mob_ad_link = mob_content.split('><')[1]
          end

          if !mob_ad_link.empty?
              # display AdMob Ad
              mob_link = "<a href='" + mob_ad_link + "'>" + mob_ad_text
+ "</a>"
          else
              # no AdMob ad, display alternate
              mob_link = mob_alternate_link
          end
      else
          mob_link = mob_alternate_link
      end

  rescue
      # no ad or server returned and invalid response code
      # display alternate link
      mob_link = mob_alternate_link
  end
%>

<%= mob_link %>