Five eggs is too many

I would have to agree with Tim33 on the first part. But I must ask why would person A ask 'how many' and then switch to saying 'too much'? On the second part, 'Five eggs are too many' is correct because of subject-verb agreement. Because the subject is plural, the verb is plural.

Unlike Tim33 and Jasper, I have no problem with 'five eggs is too much' - once you've broken them into a mixing bowl, we are talking about an uncountable mass, not separate eggs.

Nor do I have any problem with the switch from 'many' to 'much' for similar reasons. You can really only use 'many' to ask the question, but either is valid as an answer - 'that's too many (eggs)' or 'that's too much (mixture)'. - 'How many sugars do you take in your coffee? Four?' - 'Four! No, that's far too much.'

As for singular or plural with 'too many' after a number I think that there are many exceptions to the rule - "Because the subject is plural, the verb is plural" - depending on whether we see the plural noun as representing several units or a single entity, especially when numbers are involve.In all these examples, I'd argue that a plural verb would be incorrect:

'Five miles is a long way to walk for a young child.'
'Ten pounds is a lot to pay for what is basically a sandwich.'
'Twenty kilos is about the same weight as two buckets of water.'
'Thirty cigarettes a day was about his average.'

We are seeing the number here as a total amount, rather than individual units - in maths we'd always use singular, I think - 'Five is more than three' etc.

In fact, there seems to have been an settling in favour of number + 'is too many' since the late sixties:

http://books.google.com/ngrams/graph?content=five+is+too+many%2Cfive+are+too+many&year_start=1900&year_end=2000&corpus=15&smoothing=3&share=

On Google 'five is too many' gets 138,000 hits, "five are too many" only 21,000.
At Google Books it's 1,960 ('is') to 644 ('are')

Netspeak, a collocation tool, which finds examples in the British National Corpus, only appears to find examples with "is" (click on the + sign to see example sentences) - http://www.netspeak.org/#query=five+%253F+too+many

So, jayles - I think 'Five eggs is too much' is fine and the most natural answer, being the way we usually talk about food. Second choice would be 'Five eggs is too many' or perhaps better - 'That's too many eggs'. And I totally agree - 'Five eggs are too many' does not sound natural English to me, nor does it seem to be used very much.

@Skeeter Lewis - you pipped me at the post. I hadn't seen your (rather more succinct) answer when I posted.

@Warsaw Will,

Ah, I forgot about numerical S-V agreement. And that is only if you see the eggs as a single unit, I just don't see 'five eggs' as being a unit. However, just adding something makes it a little clearer:

"Five eggs is too many [to use]"
"Five eggs are too many [to use]"

Both sound rather fine to my ear with the addendum above.

I answered in the spirit of the question, but actually, I don't really find any of the answers with "Five eggs is/are too many/much" all that natural. I think I'd be much more likely to say something like "Five eggs! That's far too many/much for one person!"

I have to agree with Warsaw Will and Jasper on the subject-verb agreement in terms of singular vs. plural. In my opinion "five eggs IS too much" is perfectly fine just as the singular form is correct for the other examples Warsaw Will gave; this is because our minds subconsciously fill in additional words that are a part of the sentence structure, but not said out loud:

'[A distance of] Five miles is a long way to walk for a young child.'
'[A payment of] Ten pounds is a lot to pay for what is basically a sandwich.'
'[Weight of] Twenty kilos is about the same weight as two buckets of water.'
'[The amount of] Thirty cigarettes a day was about his average.'

I also agree that, in my mind, the eggs are a part of a liquid amount because they all go into the same bowl, in which the content increases and decreases by adding or subtracting an egg, just as the can of gasoline increases and decreases by one or two gallons of gasoline. Which is why "too much" sounds correct and according to grammatical rules, even though it is technically probably not grammatically correct.

I would dig a little deeper into that, once English is the liveliest language in the world, therefore, its grammar and vocabulary is in constant change and updating. I take it from my own personal experience as a native speaker of Portuguese where what we say very often differs from what there is in our Portuguese grammar.
The grammar of a certain people often changes through oral use by its speakers over time and often starts to change based on a mistake. Thus, what starts as a mistake, is very likely to become grammatically accepted if used by many people over a long period of time.
For now, I would stick to the countable and uncountable notions when writing but when speaking I'd probably go with Warsaw and say something like: "Five eggs! That's far too many/much for one person!"
After all, we must never forget that Oral and Written communication are quite different.

5 eggs are too many

"Five eggs is too much" is fine.

These sorts of arguments about language always remind me of that old army staff college line: "That's all very well in practice but how would it work in theory?"

I stumbled on the following at

http://www.writing.utoronto.ca/advice/english-as-a-second-language/expressions-of-quantity

"Expressions of time, money and distance usually take a singular verb:
Ten dollars is a great deal of money to a child.
Ten kilometres is too far to walk.
Six weeks is not long enough."

English is a living language!

@Maigida
I agree that English is a living language, however one should never underestimate the power of stupid people.

@Hairy Scot - I thought you'd gone AWOL! Care to explain (in a language context)?

@WW
Was in The Auld Country for a month and stayed away from PCs and other electronic gizmos.
:)
As for my comment; just my cynicism creeping through.

In a French omelette you should only use 1 egg.

...because in French, 1 egg is un oeuf.

@Thredder - Mais ca, c'est pas logique! Pour une personne on a besoin d'au moins deux oeufs, n'est-ce pas? Sorry, but I don't follow your logic. Or am I missing something?