Halacha l'ma'aseh (I think many are not aware of this)
Those who truly appreciate fine wine (בדאבוני אין אני בכללם) are very particular about avoiding wine that is mevushal because it ruins the taste of the wine (which is exactly why it is permitted). At a simcha many prefer to serve the best and finest of wines, which is often not mevushal. Of course, they will be willing to spend on shomer shabbos waiters who are going to be pouring the wine. Is this sufficient?
When we discussed earlier on this blog some questions an answers about yayin nesech, this question was touched on and is worthwhile revisiting. The gemara in the daf today discusses the issue of nitzuk - attachment by pouring. Although in the context of mikva we pasken that it doesn't create an attachment, the gemara discusses the statement of Rav Huna who claims that in the context of yayin nesech we do consider nitzuk to be an attachment. Assuming we pasken like R. Huna, the result will be that when wine is poured into the container of a non-jew containing drops or residue of wine which are assur (because they touched his lips when he drank), the flow of wine will connect the entire bottle to the wine in his glass and render all the wine in the bottle to be yayin nesech through nitzuk. The application of nitzuk to the case of the few drops of residue seems clear both from the gemara 71b and 72b. Rashi paskens like R. Huna that nitzuk is an attachemnent, but Rabbeinu Tam disagrees. Tosafos says that in the case of a significant loss (such as pouring from a barrel where there is a large quantity of wine, or perhaps when the bottle of wine is very expensive) one can rely on rabbeinu tam in retrospect that the wine in the bottle will not be assur. However, if it is not a major loss (and certainly lichatchila) we must be machmir for rashi that nitzuk is an attachment. Another point to rely on is that if the wine in the bottle is greater than the quantity of yayin nesech in the goy's cup, it would be batul in 60x, but one can not rely on bitul l'chatchila. Therefore, one cannot have a shomer shabbos waiter pouring non-mevushal wine at a simcha into the cup of a goy (or non-shomer shabbos) because when they ask for a refill, the residue in the cup of the goy will make the entire bottle assur. The only solution to this problem is to have the wine poured into glasses in the kitchen and served in glasses to the guests, so that there are no refills without washing out the glasses.