I'll try answering your Question from the perspective:
Is it Ok to ask whether something is haram if we have the hint of a doubt about it being halal?
Different levels of knowledge -> different levels of Questions
First let me tell you that even if Allah in the Quran is addressing people who use their mind and who therefore should do their best to gain knowledge and use the gifts of Allah (tongue, hands, feet, mind ... etc.) to do this and to get to know what Allah has forbidden or what He has allowed and the Quran invites us to this in many statements. Many Muslims today are -unfortunately- Muslims by tradition, I've encountered Muslims in Muslim countries who pray in a way I would qualify as invalid so my hope for them was always that Allah accepts their prayer (hoping it is from the heart) not their "movements" and stages of the prayer as it is defined in big volumes of fiqh. Note that scholars in the golden ages have defined a minimum of knowledge a Muslim should have, but unfortunately even if later some scholars even have made summaries of this knowledge which can be recited as rhymes etc. a majority of Muslims doesn't even reach this level of knowledge.
So people like this may ask about almost anything: A funny thing I've been told is that in some Muslim countries about everything has a "halal" stamp on it (I think some people have quoted Indonesia as an example, but I'm pretty sure to have seen it also in Turkish markets in Germany, even if the food or whatever is clearly something we know is halal, Andrew Grimm has already posted a Question about a halal stamp on a water bottle in an Airplane here on ISE). Of course as a person who is able to read and has some knowledge about his\her religion we would find such questions either boring, strange or one could even use inappropriate qualifications, but be sure that -some if not most- people don't ask them for fun or to mock, but they have doubts, waswas, no or little knowledge and they are invited to ask by the Quran (16:43).
On the other hand we are asked not to ask too much this is an indirect conclusion of many scholars about the statement of (5:101-102) (for details read What is the context of verse 5:101-102?).
For those people who are able to read and understand Quran in first place and in some cases the sunnah tells us what Allah has forbidden. Therefore scholars have pronounced a legal rule saying (this is the first rule among the rules of fiqh):
الأصل في الاشياء الاباحة, ولا تحريم إلا بنص
Meaning: By default anything is allowed or permitted (halal, mobah) nothing is forbidden unless we have a -clear- text (Quran, sunnah) saying so!
This means if we don't find a hint about something being forbidden we should go ahead and consider it allowed, as Allah says (5:87):
O you who have believed, do not prohibit the good things which Allah has made lawful to you and do not transgress. Indeed, Allah does not like transgressors.
Can we -as laymen- really always be sure that something is haram or halal?
In the Quran we have been told about of a lot of things which are unlawful or prohibited there the statement is clear, so anything the Quran declares as forbidden, unlawful is clearly haram. In hadith this qualification may differ in some cases, so at this point you may need help of a scholar. As for example you may find a contradiction in hadith, maybe because the statement has been abrogated, as we have also abrogation in Hadith not only in the Quran. And mostly the statements in hadiths are not that clear, so often you won't conclude directly a prohibition but it could be something frowned upon. So here you interpretation or misinterpretation of words may be a cause of a false conclusion. Also in some cases the Quran makes a general statement maybe it needs some more analysis to check what -in our time today- can be included or excluded in that statement!
So asking Questions about halal and haram will always stay up to date even if in some cases the answer could easily be found in the Quran, because this depends on the knowledge base of the Questioner himself.
The Quran gives us a general statement about what is halal and what is haram in (7:32-33) especially the later verse says:
Say, "My Lord has only forbidden immoralities - what is apparent of them and what is concealed - and sin, and oppression without right, and that you associate with Allah that for which He has not sent down authority, and that you say about Allah that which you do not know."
So we could conclude that anything which Allah considers as haram as something which might either cause harm, or be considered as bad by us humans or whatever is related to association or disbelieve! And we could conclude that anything else is halal.
Therefore in similar cases I'm trying to ask the poster what makes him think such and such is haram, because one needs to analyze the reasoning to be able to correct these false thoughts hoping this would help him/her in the future.
See also Why is halal/haram important to Muslims?.