If I understand correctly, that is exactly what Kaching (now wealthfront) did in the beginning. I've heard of a couple of other startups doing basically the same, but the only one that ever had any traction AFAIK is kaching.
There's a regulatory minefield out there that would have to be cleared, e.g., if I myself am sharing my portfolio, I would need a really good opinion that I'm not on the hook for going "investment advice" by the SEC.
Also, I subscribe to a couple of investment newsletters - I might be in violation on their TOS if I "publish" their advice automatically, even if I keep their analysis to myself. Completely automatic publishing would be unacceptable for me - it needs to be at least screened by ticker / market, and probably at the individual trade level.
I don't know much about investing, but want to get into it more and thought that something like this would be really helpful to someone like me. What sort of "regulatory minefield" are you talking about? That sounds ominous.
And with investment newsletters, you buy stock based on information that they sell you, but it's your choice right? Would you really be in violation of their terms?
Basically, there's a fine line between "giving information" and dispensing "investment advice". The former is protected by the constitution. The latter is regulated by the SEC, and requires you to be certified to do that (and there are similar requirements in all western countries).
In other words, if you in any way say "I think you should buy this", you raw afoul of the SEC, but just saying "I just bought this, and I think it's a good idea" you probably don't.
Now, would a service like that describe need SEC certification? Would the individual contributors? It can be constructed in a way that wouldn't, but that's far from trivial to either build it that way, or to even be convinced that it is for a contributor.
and re:"the violations of their terms", I meant their copyrights and the TOS you sign on. If I re-publish it (even if it's just by showing the whole world what I did), I might. It's not enforceable, but probably legal, and many such publications assert that you are not allowed to redistribute their advice in any form.
So based on what you said (since I really have pretty much no knowledge of my own) this sort of thing MIGHT be a good idea because they are indicating that the users would just see what trades other people are making. In a comment further down they mentioned that "The data would be entirely made up of trades, no opinions, comments and noise". If that's the case and there is some kind of disclaimer saying that nothing is investment advice, then no one would be liable right? Or am I oversimplifying?
I guess the only other thing I would worry about would be ending up trying to learn from someone who has as little experience as I do.
I'm not saying it MIGHT be a good idea. I'm saying it MIGHT be permitted by SEC rules, or it might not. I do not know enough about the legal side of these things, except to know that it's a minefield, nothing is as simple as it seems, and that I would consult my $500/hr SEC specialist attorney about matters such as this before I make any information available.
I feel like if I don't know how large a position someone is purchasing, the whole intended purpose of this activity becomes rather futile: There is a distinction between a person buying 1 share of Zynga vs. 100000 shares of Zynga and that gets obscured.