I said I'd offer some proof... here's a convenient article. From this month's Journal Of Trauma:
"Safety Evaluation of New Hemostatic Agents, Smectite Granules, and Kaolin-Coated Gauze in a Vascular Injury Wound Model in Swine
Kheirabadi, Bijan S. PhD; Mace, James E. MD; Terrazas, Irasema B. MS; Fedyk, Chriselda G. MS; Estep, J. Scot DVM; Dubick, Michael A. PhD; Blackbourne, Lorne H. MD
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Results: No differences were found in baseline measurements. Thrombelastography showed similar hypercoagulability of the final blood samples when compared with baselines in all groups. All vessels treated with KX or CG were patent and had no thrombus or blood clot in their lumen. In contrast, seven of eight carotid arteries and six of eight jugular veins treated with WS developed large occlusive red thrombi and had no flow. Small clots and WS residues were also found in the lungs of two pigs. Histologically, significant endothelial and transmural damage was seen in WS-treated vessels with luminal thrombi and embedded WS residues.

Conclusion: WS granules caused endothelial injury and significant transmural damage to the vessels that render them nonviable for primary surgical repair. The granules can enter systemic circulation and cause distal thrombosis in vital organs. More relevant in vitro and in vivo safety tests should be required for clearance of new hemostatic agents."

Obviously edited out the gist of the article. Everything is quoted however. Yeah, small sample size, some small study flaws, but provides some evidence for my original post.