Beacon requests sent via HTTP GET are limited to 2048 in some browsers and we have hit this limitation in our implementation. This results in a loss of data. Google is addressing this by implementing client side POST support. http://analytics.blogspot.com/2011/04/leading-industry-with-tracking-code.html
This would be a very powerful feature and make us use Omniture for even more purposes. I imagine it would also improve data accuracy for many clients who could be inadvertently going over the limit.
This is solved with AppMeasurement 1.4.1 and the Visitor ID service.