Unfortunately, that would often break. We've put a lot of effort into URL normalization (ie, http://smile.amazon.com/TP-Link-TL-WA701ND-150Mbps-Wireless-... is the same as http://www.amazon.com/dp/B002YETVVE/). When we can do "good enough" on the client so we can provide the same benefits, we'll do it. Or: provide a setting that forces URLs to exactly match, and we can use a bloom filter to keep traffic down.