Investing in bitcoins (or other cryptocurrencies) is no different to investing in dollars, euros or any other currency except for the sizes of the falls and rises in value which can occur. (e.g. if you spend lots of money buying euros you might expect the value of your investment to gradually creep up or to gradually go down. You wouldn't expect it to halve, or to double, almost overnight, as can happen with bitcoin investments).
So, as long you're prepared to take bigger-than-usual risks with your investments, ther's absolutely nothing wrong with buying into bitcoins, per se.
However there are plenty of scam websites around (e.g. Bitcoin Trader) that promise to help you put your money into bitcoins but where you'll end up losing everything. Such sites often falsely claim to be endorsed by well-known figures. (Martin Lewis, from the Money Saving Expert website and BBC TV, is constantly having to fight to prevent unscrupulous firms saying that he's endorsed their dodgy services).
If I'd got money that I could afford to put at risk I'd most definitely be buying cryptocurrencies. (e.g. if I won £50m on the Lottery, I'd use £1 or £2m to make such speculative investments). However
(a) I'd probably not buy into Bitcoin, per se. There are many newer cryptocurrencies which potentially offer far higher returns ; and
(b) I'd not use any money that I couldn't afford to lose to make such investments.