This works great, except that some sites seem to block requests from EC2 hosts. StackOverflow and Yelp are two that come to mind immediately although I'm sure there are others. If I remember right, StackOverflow only lets you access via the API if you're on an EC2 host.
On the other hand, I can see where they're coming from by banning the whole netblock. Otherwise you could scrape until your IP get banned for blowing a rate limit, then tear down that instance and spin up a new one.
I get this same message about once a week since I frequently use my Linode VPS as a proxy for my web traffic, but it's never lasted for more than a half hour or so. I've always wondered why their heuristics only seem to notice me so infrequently. Do you get it consistently?
Yes, I have never been able to access Google from my Slicehost VPN IIRC. I also used a Linode VPN for a while and got the message infrequently with the possibility to enter a CAPTCHA to complete my request.
I also connect a lot through an EC2 machine that I use as a proxy. I do this because I do not live in the U.S. and many websites require U.S.-based IPs.
It's a pity that StackOverflow doesn't allow me to do this (so I end up turning the proxy on and off and back on again). It's not like you couldn't rent a cheap Linode instance (or from another provider, take your pick) and do whatever you want with SO, if you really wanted to.
SO needs more sophisticated tools to block the access for bots/crawlers. IP blocking just doesn't cut it and tends to discriminate against legitimate users with special needs.
On the other hand, I can see where they're coming from by banning the whole netblock. Otherwise you could scrape until your IP get banned for blowing a rate limit, then tear down that instance and spin up a new one.