Ron Conway's a 'specialist', so tends to have less of a broad appeal. They are influential, but only in their circles. For example - I've never heard of this person until I read your post and did some digging. So a 50sish score is about right. Compare that to media celebrities who are known throughout the western world, it's interesting.
It's only real flaw is that it does not take into account any kind of print or televised influence, only social media. And even then, unless you explicitly connect them, it only looks at twitter, even if you are influential in other medium (+David Seaman
has this problem, since he posts a lot on Google+ but hasn't linked it to Klout, so his Klout score only reflects his Twitter useage.)
Since marketing is starting to slant extremely online (even more so with each passing year), it makes sense for marketers, as described in the OP, to need a high Klout score. If they can't market themselves
online, how would you expect them to market your products?