One thing that worries me about Siacoin is that increasingly more cryptocurrencies are offering the same ability. Whilst SC specializes in cloud storage these other cryptocurrencies are often platforms that can do much more, as well as cloud storage. Perhaps Siacoin can outperform the others by specializing though.
At the current price I do think Siacoin is an interesting investment to put a small amount of your portfolio in.
One has to keep in mind the maximum potential too. Although Siacoin will surely grow, I don't think it will ever be as big as an Ethereum. This limits the maximum amount of profit you can expect. Siacoin is for 1-10x gains, not for 100x gains, I believe.
RE: Why you should be careful by investing in SiaCoin!