Tracking Query String and Linking

do query strings (...com?p=123) hurt linking efforts

[barnetap]

When conducting more traditional advertising, I've traditionally employed query strings in an attempt to both track the effectiveness of the advert and benefit from another link. An example would be:

[widgets.com?Promo=1234...]

While technically a unique URL (i think), there certainlly are plenty of examples of these type of URLs being detected by Google. But, is there any "penalty"? Are these not as effective as "straight" links?

Also, should I concentrate on building more "deep links" instead of pointing them at the top level domain?

[badtzmaru]

I am currently of the opinion that they are not as effective as direct links. The extent to which this holds true seems to vary ever so slightly from month to month as google seems to tweak the algorithms almost constantly now.