There's a difference, though, between "acting helpless" and "being in need of aid".
I find it incredibly offensive when anyone acts helpless -- pretending as if, without immediate help, they would be utterly lost and confused and possibly in very real trouble, as if they could not take adequate care of themselves without the help of someone else. It's perfectly fine to genuinely be helpless every now and then -- it happens to everyone. But I view the deliberate feigning of utter incompetence at something the person is actually half-decent at, especially when it's mission-critical, as an insult to the intelligence of the target, an insult to the collective competence of the gender so misrepresented, and a "crying wolf" effect.
If I need some help shoveling my car out of a phreaking ditch, I need some help shoveling my car out of the goddamn ditch, and not some testosterone-crazed twits shoveling me out and then proceeding to mack on me like there's no tomorrow because they have assumed it was a blatant ploy for attention.
As far as the in-need-of-aid flirtation strategy goes, I like to pick something that I know the target to be interested in and good at, yet not mission-critical, so they have a real choice at whether or not to come to my aid, rather than a situation where the only decent thing to do is to give aid. Since I go for geekboys, and I want the kind of geekboy who is attracted to geeky girls, I want to appear in need of minor aid in such a way that I display my true competence as well.
Perhaps I have a buggy program, and I haven't tracked down all the errors yet. I am capable of doing a lot of that myself (and everyone needs a little help on the stubborn ones), but it's always nice to get a second opinion. I could solicit the second opinion from the passing cute guy. Maybe my layout is a little funky, and I really want to know which way it looks better, this way, or that way. Or maybe it's something physical. I'm changing a tire, and my arm strength might be a little sub-par to get the air-wrench-tightened nuts off on the first try. I could give the lever a good kick, or I could tell the person who's just pulled over to see if I need some help that yeah, I could use another bit of muscle over here; it's already jacked up and ready to go...
This may exaggerate my need of aid a little, but it's legit, and it's a strategy that offers a person a choice of whether or not to help. It should be an opportunity for aid, also, that allows them to excel at something they do well. Not only do I get the assistance I need, but they get to show off any prowess they may have. I would not ask Darkside, say, to display his strength by helping me change a stubborn tire. He is tough, but we both know that I am stronger. (The last time there was tire-changing going on with the two of us, I was the one who stepped in and got his nuts off when they proved too stiff for him to handle.)
Another, pressing, reason that I don't like using a situation of helplessness as an opportunity to flirt is that it may set up an atmosphere of expectation or entitlement on the part of those who have just played the part of Knight in Shining Armor. They have done their part in rescuing the lovely swooning maid, and now they want their reward. A more difficult rescue usually demands a larger reward, and for an initial flirtatious move, I do not want help that requires more than a smile and a heartfelt "Thank you!" in return. After all, much of the time, I wouldn't actually know them, especially if the situation is a "getting your attention" or "getting to know you" social maneuver.