Behavioural Ad Targeting

What are people's feelings toward behavioural ad targeting?

I am genuinely interested in this area as I attended a recent event held by the Internet Industry Association, hosted by Baker & McKenzie, Sydney and found some of the issues discussed very thought provoking.

For those of you who are unfamiliar with behavioural ad targeting, it offers online publishers and advertisers ways to increase the effectiveness of their campaigns by tracking individual's web-browsing behaviour and in so doing, offer online ads that the user is most likely to be interested in.

There are many issues around this topic, including but not limited to:

1. the issue of consent
2. how sensitive user information is used / stored (and for how long is data retained)
3. how is the opt-out of the service managed
4. what safeguards can be placed on the aggregation of user centric behavioural data and on the manner it is to be used
5. tests around whether anonymity of the data is preserved or not

ANYWAY - Interested in what other practitioners think and what YOUR views are.