Are social media TOS invalid because lack of due process and mutuality
creates an unenforceable illusory contract?
No.
The American Bar Association has a nice distillation of the state of the law with respect to terms of service, and I reproduce the most relevant portions of that analysis below:
Are my terms and conditions enforceable?
Courts are now regularly enforcing so-called "click wrap" agreements,
where a user's assent to the terms and conditions posted on a website
is rendered by clicking on a button that says "I agree" or "yes". When
these agreements are upheld, users are deemed bound by the terms in
the same way that they would be bound by a signed contract, whether or
not they actually read the agreement, so long as there was an adequate
opportunity to do so. Requiring the user to expressly agree or
disagree with the terms and conditions posted on a website goes a long
way to ensuring that an enforceable contract was created. Whether
posted terms and conditions that do not require the user to click an
"I agree" button can create an enforceable contract. is less certain.
(See "Can I simply post terms and conditions?")
Yet, even where an electronic agreement requires express assent, there
are still reasons why a court may not enforce it. A court will
consider whether the terms were presented in a way that provided
reasonable notice, i.e., Was the typeface legible? Was the full text
of the agreement easy to find? Was the text, even if large, easy to
understand? Another element of adequate notice is whether the user was
made reasonably aware that it was agreeing to a contract, i.e., was
the button meant to indicate assent designated as "I agree" or "Yes",
or in an ambiguous manner, such as "submit", "continue" or "show me
the lenders?"
To increase the prospects of enforcement, website terms and
conditions, like all standard form contracts, should be drafted in a
clear manner, without technical jargon and excessive legalese. Thus,
care should be taken that terms and conditions are not unduly long by
virtue of irrelevant clauses or extraneous boilerplate. They should
also be presented as legally-binding terms, and not mixed with
marketing messages, and they should be scoured for inconsistencies
with other statements made on the site. It is also important that the
site allows the user adequate time to review to terms, both when first
presented with them and for later reference. (For other factors
relating to the presentation of terms and conditions, see "Are
electronic contracts enforceable?" and "Can I simply post terms and
conditions on my site?")
Terms and conditions should be capable of being retained by the user
in electronic or printed form, if they are not being sent directly to
the user by another means, such as by mail or fax. Some industries,
such as financial services, are required to provide copies of
contracts to the user in hard-copy form. In addition, as to electronic
transactions generally, Section 8 of the Uniform Electronic
Transactions Act, adopted in some form in nearly all 50 states
("UETA"), prohibits a website proprietor from inhibiting a user's
ability to store or print the contractual terms if the parties have
agreed to contract electronically and the law requires that the user
be provided information in writing. One might expect the same
requirement in other jurisdictions even without UETA. Under Section
101(d)(1)(B) of the Electronic Signatures In Global and National
Commerce Act ("E-Sign") terms and conditions must remain available to
the user, in a form capable of reproduction for later reference, if
the applicable law requires that a record be retained regarding the
transaction.
In order to avoid errors that result from typos or improper navigation
of the site, the user should be able to view and approve an order
summary or confirmation screen prior to the placement of an on-line
order. In fact, UETA Section 10(2), gives an individual the right to
rescind a website transaction resulting from his or her error if there
was no opportunity to correct it, assuming that the individual
promptly notifies the seller of the error, takes reasonable steps to
return or destroy any product or service received, and has not used
any benefits provided.
Finally, an issue that underlies all standard form consumer contracts,
which are presented on a "take it or leave it basis," is whether the
terms are so unfavorable as to be considered "unconscionable" and,
therefore, unenforceable, regardless of whether the customer has
manifested his or her assent to them. (See "What provisions are not
enforceable?")
A 2021 article from the New York Times explains that for the most part, Terms of Service are enforceable and that any regulation of limitation of them will require regulatory or legislative intervention.
As noted in another answer, "due process" is not something that a private business, as opposed to a governmental entity, is required to afford you.
A ToS is generally not invalidated either on the ground of lack of mutuality or on the ground that only one side is bound to perform (and the website with a ToS is usually providing something of value to the user, so it isn't truly one sided).
One fruitful way to understand a ToS is that it legally defines the intangible product that the website or online service is providing.
