well i don't know if hoodoo doesn't backfire or not, all spells carry the potential of backfiring, or at the least not working, for many different reasons. love spells are tricky though, and it can be classified as "black magick" since many love spells are used to force someone to fall in love with the caster unwillingly. if you're planning on casting this type of spell, be warned, you will feel some negative karma coming your way. also, spells ware off, and love spells have to also deal with the person subconsciously fighting against it. so a spell might ware off in a day, or ten years, it all depends. if i were you i'd research, and meditate on the issue, before casting a love spell. if you wanted to cast a simple one to attract love into your life though, lighting a pink or red candle while visualizing yourself with someone [but not a specific person] that would be ok, since you're not casting over someone, you're sending the energy out to bring someone to you.
if you cast be sure to be proactive, don't sit around waiting for something to happen, talk to new people, go to social events, that sort of thing.
Here's my two cents on the matter of Love spells or workings:
I don't care if you do them or not. It's not my problem. However, one thing about Hoodoo workings is that are they justified or not? Because when they don't work out it's most likely because it's not justified. You find out through divination. The spirits will let you know. If spirits say it's okay to do so, do it.
The other thing is do you know how to make a honey jar? It's not throwing things and a sweetener in a jar and then burning a candle on top. It's a matter of praying over the herbs, talking to them. Adding them to your sweetener, along with other things. Sealing that jar, praying over it. Keeping it warm, keeping it working. You're asking for something such as love or someone to be sweetened to you.
Now as far as backfiring goes, how do we know when a spell truly backfires? Or if it does backfire? To me, it just seems like things aren't going well in a relationship, and it ends. Perhaps they don't take interest anymore, and don't want to be in the relationship. That would be their choice, and not something a spell "backfiring" would do in my opinion. The spell itself did what it was supposed to do, but after that maybe things just aren't working out?