The only reason I bought bitcoins for what I consider ridiculous high prices was to speculate with alt-coins.
I actually bought quite a few of them, which I never would have bought as I think the price of bitcoins is way too high and overvalued, and you're not going to make any money at these price levels, at least not worth the risk.
I didn't sit on many of them, but the fact that I bought them and transferred them to someone who essentially created new wealth for bitcoins with the alt-coins, definitely was bullish for bitcoins. Of course if the person who I gave my bitcoins to immediately sold the bitcoins for cash it wouldn't have much effect but I am sure most people who made money/bitcoins from selling alt-coins held onto them.
So my thinking goes now that alt-coins are pretty much dead and that whole speculative alt-coin boom looks to be over, this will really hurt the price of bitcoin. Basically the alt-coins were creating new wealth for bitcoins, a big reason for someone to take fiat and dump them into bitcoin to get part of this new wealth. This is pretty much over in a big way right now.
Anothing point is the bitcointalk forum was looking at completely getting rid of the alt-coin sections at one point, but they decided to keep it and expand it. I think the reason they expanded it was that they knew the alt-coin boom was really helping bitcoin as that is the only thing most people would actually buy with their bitcoins.
My point is that this alt-coin crash is actually a very bad thing for bitcoin in my opinion. I think that was a big reason why the prices were held up for so long. I know I personally put thsouands of dollars into bitcoins because of this reason alone and I am very frugal. You can imagine what the degenerate gamblers must have put into it.
Fads come and go.
These hundreds of Alt-coins were nothing but a FAD and now I suspect we have crypto-currency fatigue setting in. The vast majority of these Alt-coins will vanish into obscurity, a few will remain. Litecoin being the only odds on certainty to still be around and relevant for some time to come. The USD volume of these Alt's however were generally so low, I doubt that it had much of an effect on Bitcoin.
I think it is rather more the crypto fatigue that is centred around exasperation and disillusionment with Bitcoin that is proving bad for the Alt's, other than the other way around. None of these Alts have any uses whatsoever outwith speculation. Speculation that was always based on euphoric visions of Bitcoin's potential and now that this euphoria has subsided and been replaced by apathy, the Alt-coins are seemingly totally irrelevant.