Here's something more interesting.

Bitly vs tiny.cc

I used http://web-sniffer.net/ to grab the headers of both and with bitly links, I see an HTTP Response Header of 301, followed by "Content", but with tiny.cc links I only see the header redirect.

Two links I'm testing:

http://bit.ly/M5onJO

http://tiny.cc/s2i6ww

Bitly response:

Content (0.11 <acronym title="KibiByte = 1024 Byte">KiB</acronym>)

<title></span>bit.ly<span class="tag"></title>

 <a< span="">href="https://twitter.com/KPLU">moved here</a<> 

I wonder why you're seeing a 403, I still see a 200.

http://www.wlns.com/story/24958963/police-id-adrian-woman-killed-in-us-127-crash

200: HTTP/1.1 200 OK

• Server IP Address: 192.80.13.72
• ntCoent-Length: 60250
• Content-Type: text/html; charset=utf-8
• Server: Microsoft-IIS/6.0
• WN: IIS27
• P3P: CP="CAO ADMa DEVa TAIa CONi OUR OTRi IND PHY ONL UNI COM NAV INT DEM PRE"
• X-Powered-By: ASP.NET
• X-AspNet-Version: 4.0.30319
• wn_vars: CACHE_DB
• Content-Encoding: gzip
• Content-Length: 13213
• Cache-Control: private, max-age=264
• Expires: Wed, 19 Mar 2014 21:38:36 GMT
• Date: Wed, 19 Mar 2014 21:34:12 GMT
• Connection: keep-alive
• Vary: Accept-Encoding

I looked at all 3 redirects and they all showed a single 301 redirect to a 200 destination for me.  Do you recall which one was a 403?

Looking at my original comment in the question, last month bit.ly had 10M results and now I'm seeing 70M results, which means there was a [relatively] huge increase with indexed shortlinks.

I also see 1000+ results for "mz.cm" which doesn't seem much strange, since mz.cm is just a CNAME to the bitly platform.

I found another URL shortner which has activity, http://scr.im/ and I only saw the correct pages being indexed by Google, not the short links.  I wonder if the indexing is particular to bitly and/or the IP subnet behind bitly links.

I looked at another one, bit.do, and their shortlinks are being indexed.  Back to square 1.

I spot checked a few and I noticed some are only single 301 redirects.

And looking at the results for site:bit.ly, some even have breadcrumbs ironically enough.

Here are a few examples

<cite class="_md">bit.ly/M5onJO</cite>‎

bit.ly/O6QkSI

bit.ly/18HZSgo

None of these should be indexed, but for some reason they are.

Presently I see 70M pages indexed for "bit.ly"

I see almost 600,000 results for "bitly.com"

I did a quick search for "site:bit.ly" and it returns more than 10 million results.

Given that bit.ly links are 301 redirects, why are they being indexed in Google and ranked according to their destination?

I'm working on a similar project to bit.ly and I want to make sure I don't run into the same problem.

I've been looking at some bigger enterprise sites and noticed some of them used HTML like this:

<a <="" span="">data-href="http://www.otherodmain.com/" class="nofollow" rel="nofollow" target="_blank"></a>

<a <="" span="">Instead of a regular href=""

Does using data-href and some javascript help with shaping internal links, rather than just using a strict nofollow?</a>