Yet getting good beta testers is hard. Many people sign up, use it once, hit a bug and then never return. Understandable, but even emailing people (personally) hasn't been all that effective in getting people back consistently. I probably have 10 people that I can keep going to and know that they will use it again and again and provide feedback.
I've yet to go on a strong blog push yet, but thats probably my next approach.
Other methods to find bloggers: YouTube and Twitter Search. I've also been looking through friend's shared stuff on Google Reader occasionally to mark off ones to contact.
One twist that I have as problematic is that I don't have and 'special codes' to hand out to people currently. We had a system setup like that a while ago, but I think it was slowing downloads a bit so now its just a download link and you register for a (free) account in-client.
In addition for ideas of how to get more testers via blogging (commenting is important I know too), anyone trying it out would be really appreciated. I'm going to have them push the newest build to our download and auto-update servers later today.
Edit: Also, how you computed readership numbers for a blog?
As for computing the traffic numbers, first look to see if they have a media kit on their page or an RSS subscriber badge. Then look at the number of inbound links on Technorati and Google. Then check sites like Alexa and Compete. Also check the number of comments on the site, if there are any. Pay attention to the quality of the posts themselves. Are they writing original ideas, like Fred Wilson, or are they mostly regurgitating the results of PEW research studies? Have they won any awards? And lastly, take into account what platform they're on. A Typepad blog is going to have different traffic patterns than a Tumblr blog, simply because of the ecology of the platform and the userbase.
Using this you should be able to get a pretty decent estimate of the readership, especially once you have 10 or 20 blogs where you have exact data to use as a benchmark.
Our pitch email subject line was a brief description of the product then "- Free demo codes for your readers". The body had a similar format: what we do, here's your code, contact us with any questions, thanks.
Lots of sites have feedburner badges to give subscriber counts. We found one blog that was clearly faking that though. Their traffic to us was way lower than an 80k subscriber blog would send.
The number of comments on posts is a good indicator too. Anything greater than 0 means they've got a fairly big audience.
Nice hack and something I appreciate because it's such a simple thing to do.
"... Lots of sites have feedburner badges to give subscriber counts. ..."
Did you try to obtain the stats from each site?
Given two similar services, one with a limit on registration and one without, you can bet that the one with the limit will garner some sort of popularity just by virtue of being "exclusive."
This doesn't mean it's a bad marketing tactic. On the contrary, it's obviously excellent for exposure... but if it ever becomes a popular service, saying "I was there first" is a huge deal for people. For reference: Lines outside movie theaters days in advance for the Star Wars movies, video game midnight release parties, and 8 hour lines outside Apple stores for a phone.
It's your trending over time that really counts.
Definitely going to use this strategy in the future, but hope the reach of this post doesn't flood blogger's inboxes with similar schemes.
I've used a similar approach, but only with the blogs that I had either made personal contact with previously or that I frequented.
On another note, your blogroll/Reader subscriptions are a great place to start if you follow other bloggers in your industry. Being an active member of the blogosphere also helps give you some clout.
I get relevant press releases from time to time that are in my industry/field but are so "corporatey" that there's little my readers would really care about. Twist whatever you have to say into a story that fits the mold of what the blog already posts - it might take reading their entire front page to get a feel for this ;-)
The general pattern was mention the private code as a teaser, describe/review the service, then give the details for signing up with the code.
The biggest hits for our beta were sites we never heard of that found us on smaller blogs and reached out to us. Sites like http://www.dinside.no http://www.genbeta.com and http://www.walla.co.il.
I should write about our experience with non-english blogs later.