What do you think of emails that are triggered as a result of your browse behavior?

The key, and Dave hit the nail on the head, is frequency. If you send the customers email after email after email, it doesn't become creepy, it's annoying which means you stop surfing the website, you mark the emails as spam and post something nasty about the sender on twitter and facebook. That's marketing done wrong.

On the other hand, a well thought out triggered email that takes into account past purchasing, browsing, email opens and closes, shopping cart abandonment and demographics can yield fantastic results. Yes I say this wearing my marketer hat, but let me swap it out looney tunes style and as a consumer learning of special deals and releases from artists that I may have purchased is a good thing when you're tracking your spending.

We are past the creep in email marketing and are in the age of fine tuning our interactive marketing efforts. I encourage people to create messaging based on trackable user behavior, that's the world of tomorrow here today.

while one cannot disagrees that the Amazon targeting is clever I ma very much unemotionally subscribed to Amazon due to lack of relevance and control.

If I buy my girlfriend, mother and/or sister a present on Amazon for next 3 weeks I'm getting beauty treatment and perfume offers. I've found the only way to get them to stop is not to open the emails.

As far as I'm concerned a deeper level of profiling has to be performed to customers who are repeat buyers otherwise they can be easily alienated.

However, if the content is relevant and the recipient can go back to a preference centre and change their preferences if they do not enjoy the experience.

If it is accurate it won't be creepy, it should be cool

What you're describing is what I call the "Happy Coincidence" email.

Works great for an abandoned cart, or browsing behavior.

If you simply send an email with an offer on a product that you know has interest, without saying how you know or even implying that you know, is SUPER effective. However, if you're not smart about how you execute these, a potential customer can catch on and "game" the system.

It's why these types of emails need to have limits on frequency, and that the frequency should be changed often.

Totally creepy -- and likely illegal under CAN-SPAM, the new Canadian law, and others.

I find Amazon's emails based on my browsing to be useful. They are relevant and sent infrequently. Conversely, I've received emails from Godiva by participating in a rewards program and I found them to be quickly irritating because of the frequency in which they were sent. - I simply don't need an email about chocolate every couple of days.
My acceptance of these emails is based on the assumption that I've opted into them at least at some level (and with a clear path out of them.)

Less savvy consumers may find them 'creepy' but I suspect that there are fewer and fewer consumers who don't have some semblance of data mining at least abstractly.

Echoing the previous answers, frequency is really the key. The challenge is that acceptable frequency varies by individual. In some instances a daily update is more than warranted. In others, weekly or monthly may be appropriate if there isn't enough change to warrant that level of attention.

A good rule of thumb for email outreach triggered from web behaviors is to base it upon the frequency of your visits. If your average visitor hits your site multiple times a day, a daily summary may be appropriate. If your average visitor hits your site once a week, anything more frequent that than is likely to cause some consternation.

Experiment with longer timeframes / intervals for your communications. It's far easier to increase frequency than it is to decrease frequency. The initial bombardment will likely turn people away vs. leave them wanting more.

I agree with Dave. First, anything you put online, whether it's a photo, blog, contact info etc., is accessible to anyone and everyone. Putting your information on the web is more than likely a guarantee that you will be contacted by someone. If a site requires contact information and you do not want to be contacted, simply put a false name (eg. John Smith) and false number (eg. 123-456-7890). This way you, the customer, are not bombarded with follow up emails/calls and the individual responsible for following up with those who have supplied their information does not waste his/her time or your time.
With regards to the question about receiving information after you browse items, I find it helpful. Sometimes you may not get all of the information you were looking for and a follow up allows for an opportunity to find more content pertaining to your search. Again, if you put your contact information, it is because you wanted that information provided. I understand and agree that multiple follow up emails are unnecessary and slightly annoying, but a single email that contains relevant content often is helpful.