I think accepted helper should be earned through moderator approval, not simply thanks.
Judging just by the chance that someone does or does not click the thank link isn't an accurate judge of whether or not one should be listed as an accepted helper. I think it may also lead to abuse of the system in order to reach the required votes, be it 50 or 150.
Having that label makes one look like they are endorsed by CH as someone that people can trust, which may not always be the case. The moderators here know more or less which of us have some idea of what we're doing and that we give accurate advice and make honest, reliable contributions to CH and have a good rapport overall with the community.
Funny, as I was writing this I was looking for an example of a regular with few votes. Turns out to be me. I only have 45 votes, therefore I don't have that label. Does this mean what I say can't be trusted? Am I not an "Accepted Helper"? In my 3 years here, have I ever given negligently harmful advice? Does the fact that I haven't been thanked by a certain number of people mean that my help is not acceptable or was not effective or helpful in some way? Are Patio, Allan, Carbon, and BC, and Chris out to get me? Do I have to ignore all of you and announce it publicly in my signature? No, of course not... well, maybe Patio... who in the shadows when I sleep.
Really though, I think that kind of a label should be left to the judgement of the moderators, not necessarily the number of thanks one might have.
(Sorry, it kind of sounds like a rant, but it wasn't meant to be. Just wanted to make a point.)