Why isn't Ethereum Frontier a "safe" platform?

Question

On the Ethereum homepage, underneath the Ethereum Frontier header, there's a tag line which reads "A safe decentralized software platform", but with the word "safe" crossed out.

Is this simply because Frontier is an early-release version, and therefore comes with the expected bugs, security problems, and unknowns, or is it because certain things are explicitly and deliberately missing in Frontier which makes it inherently less safe than later releases such as Homestead and Metropolis.

(I'm not concerned with qualifying exactly what "safe" means in this question.)

Answer 1

The primary reason Frontier is not "safe" is because:

In short, we’re doing everything possible to make Frontier a safe place to test Ethereum with real value, but we are also strongly discouraging people from using Ether on the Frontier network which they are unwilling to lose.

Source

Frontier is intended largely for people who are writing and testing tooling for mining and exchanges, and perhaps a few of the more hardy dApp developers. It is not a general release that we expect ordinary users to interact with at all, although you might download a client and mine a little Ether just because you can. The show really starts at Homestead, and we’ll have more news about Homestead’s features later.

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For developers, the Ethereum blog post that introduced Frontier, also left open the question that "state in contracts is will likely be erased". Frontier has performed well to the extent that this open question appears to be resolved in the direction that the state of contracts will be safe and preserved.

EDIT: Indeed there will be no chain reset.

Many of the planned Frontier gotchas (which included a chain reset at Homestead, limiting mining rewards to 10%, and centralized checkpointing) were deemed unnecessary.

Answer 2

Currently Ethereum Frontier is still undergoing massive changes, and there are a lot of bugs and features left unimplemented.

For example, scalability is a concern and there is the possibility of changing that via the consensus algorithm (see Casper).

Also Solidity is still being fully implemented and not fully there as of yet.

Point being, it works, it's just not very user friendly ATM. There are still a lot of bugs left to fix and features needed to implement and even changes to the protocol itself. So I'd say if you know what you're doing (you know your way around the terminal) and if you go in with the understanding that certain things could be disallowed in the future that were possible before, then you should be fine.