When I was at inAsphere.com, the first thing we did after launch was "Okay, I want every staff member to create at least 5 fake personas, and have conversations with yourselves." So we created accounts and came up with backgrounds and personalities and stuff, and had mock arguments with ourselves on the forums.
I know cross-x.com started the same way, since it was by the same founder.
The only website I've been involved with which didn't seed things with a bunch of fake usernames was FictionAlley. That was largely because the site was intended to be personal, for a few friends only, and only randomly happened to catch on among the general fandom. Since it was started with more than a dozen founders, they had ample material to begin with.
I was involved with a dot com back in 2001 where I did an internship. Our first week consisted of all the staff members(there were about 10 of them) creating accounts and contributing. BUT THAT WASN'T THE SITE'S MAIN MARKETING PLAN. That is what you have to understand. Bots and fake personas have very limited lifetime; at the end you have to get real users to make your site of some worth.
But there's a difference between a site that sucks no matter what you do and a site that could survive on its own if only it passed the initial attracting-users hurdle. Reddit's a good example of the latter: I checked it out about a week after it launched, and it was really quite boring. I came back a few months later, and it actually had a thriving community. If the Reddit founders hadn't stuck with it and just folded the site, they'd be out a few million dollars.
At least when you catch some sort of fire and start getting a decent stream of traffic, it will be something you can be proud of and build on.
About dating sites using bots - states are now enacting laws to regulate that. Watch out.