Use robots deny on sandboxes as well as preview/verify.  

Googlebot started crawing sandbox-s3 very aggressively
Good question.

Here's a list of likely values for this header:

```
frank@frankdev:~/chef-repo/cookbooks$ ack-grep --all -i x-staging
_varnish/files/default/sandbox_backends.vcl
104:    if (req.http.X-Staging == "preview" ||
111:    if (req.http.X-Staging == "externaltest") {
117:    if (req.http.X-Staging == "verify" ||
124:    if (req.http.X-Staging == "sandbox-s1") {
130:    if (req.http.X-Staging == "sandbox-s2") {
136:    if (req.http.X-Staging == "sandbox-s3") {
142:    if (req.http.X-Staging == "sandbox-s4") {
148:    if (req.http.X-Staging == "sandbox-s5") {
154:    if (req.http.X-Staging == "sandbox-s6") {
160:    if (req.http.X-Staging == "sandbox-test-s1") {
166:    if (req.http.X-Staging == "sandbox-qa01") {
172:    if (req.http.X-Staging == "sandbox-qa02") {
178:    if (req.http.X-Staging == "sandbox-qa03") {
184:    if (req.http.X-Staging == "sandbox-qa04") {
190:    if (req.http.X-Staging == "sandbox-qa05") {
196:    if (req.http.X-Staging == "sandbox-rottentomatoes") {
202:    if (req.http.X-Staging == "sandbox-velos") {
208:    if (req.http.X-Staging == "sandbox-mercury") {
222:    if (req.http.X-Staging == "demo-sony") {
228:    if (req.http.X-Staging ~ "^(verify|preview|sandbox.|demo.)" ||
231:        req.http.X-Staging == "externaltest" ) {

_varnish/templates/default/border.vcl.erb
206:    if ( req.http.X-Staging ~ "sandbox" ) {

varnish/files/default/varnish-configs/border.vcl
87:    set req.http.X-Staging = "externaltest";

varnish/files/default/varnish-configs/wikia.vcl
103:    set req.http.X-Staging = "verify";
109:    set req.http.X-Staging = "preview";
860:  if (req.http.X-Staging == "preview") {
865:  if (req.http.X-Staging == "verify") {
870:  if(req.http.X-Staging == "preview" || req.http.X-Staging == "verify") {
```