I think I've found the bot that's to blame:
It's called "lj_wh0re"
Found it using LJ Seek:
How to make friends and influence people ( the quick way )
Part of the (now-deleted) explanatory entry:
"A few days ago I had 195 people on my friends of list. Now I have over 350. Why is this? Now in my moments of vanity I'd like to think my journal was more interesting or more compelling or better written or better whatever than those other motherfuckers, but unfortunately this simply isn't true. I'm lazy, I can't be arsed putting any effort into the craft and I'm not super talented in anything or a beautiful pretty girl willing to swap a sweet piece of her flesh for fame, worship and fortune. BUT... "Another telling entry: http://community.livejournal.com/h0s/5315.html
And another: http://users.livejournal.com/cyber_bard_/155200.html
And yet another: http://lok81.livejournal.com/296644.html
"It's LJ Wh0re!...For wankin' idiots who think collecting anonymous users equals popularity, it's the LJ Wh0re, from R0nco!"