I think the key wording was "uber for bouncers" and "per guard". We're not talking executive protection or major event security. An average armed guard in my city would be lucky to make $15/hr. For $35/hr you can hire an off duty police officer. A quick google shows the mean security guard salary is ~32k in SF and 75% of $36k, so even with a 50/50 split a guard working 40hrs would be making normal wages and bringing home $35k a year.

There's a ton of small events (think a 100 attendee unconference) that may be required to hire security for legal/insurance/contract reasons. Many event spaces require you to hire security whenever alcohol is served. Small events like that where showing up an hour ahead of time is plenty to figure out where the exits are, who's in charge, etc. I could see this being useful for smaller restaurants/clubs/bars that don't have an established relationship with a security provider and could use this to call in security only on the busy nights.

Of course, I also see people using this for parties at their house/office just for the image of having a party so 'exclusive' there was a bouncer. People who need real actual security will look elsewhere and pay much more.